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FM 3-34.331 

(Formerly FM 5-232) 



Topographic Surveying 




HEADQUARTERS, DEPARTMENT OF THE ARMY 



DISTRIBUTION RESTRICTION: Approved for public relase; distribution is unlimited. 



*FM 3-34.331 (FM 5-232) 



Field Manual 
No. 3-34.331 



Headquarters 

Department of the Army 

Washington, DC, 16 January 2001 



Topographic Surveying 



Contents 

Page 
PREFACE vii 

Chapter 1 MISSIONS, OPERATIONS, AND DUTIES 1-1 

Survey Missions 1-1 

Survey Operations 1-3 

Survey-Personnel Duties 1-9 

Fieldwork 1-11 

Office Work 1-15 

Survey Communication 1-17 

Chapter 2 PROJECT PLANNING 2-1 

Section I - Evaluation and Scheduling 2-1 

Project Requirements 2-1 

Unit Capabilities 2-2 

Accuracy Constraints 2-3 

Milestones 2-3 

Administrative Support 2-5 

Logistics Support 2-6 

Section II - Information-Gathering Trips 2-8 

Initial Site-Visitation Trip 2-8 

DISTRIBUTION RESTRICTION: Approved for public release; distribution is unlimited. 



This Field Manual (FM) supersedes FM 5-232, 27 September 1989, and Technical Manuals (TMs) 5-232, 
1 June 1971, and 5-237, 30 October 1964. It also supersedes DA Forms 1904, 1 February 1957; 1906, 1 
February 1957; 1908, 1 February 1957; 1910, 1 February 1957; 1912, 1 February 1957; 1913, 1 February 1957; 
1919, 1 February 1957; 1926, 1 February 1957; 1946, 1 February 1957; 1950, 1 February 1957; 1951, 1 February 
1957; 1952, 1 February 1957; 1961, 1 October 1964; 1964, 1 February 1957; 2840, 1 October 1964; 2842, 1 
October 1964; 2843, 1 October 1964; 2844, 1 October 1964; 2845, 1 October 1964; 2846, 1 October 1964; 2848, 
1 October 1964; 2849, 1 October 1964; 2851, 1 October 1964; 2852, 1 October 1964; 2853, 1 March 1968; 2858, 
1 March 1968; 2859, 1 March 1968; 2860, 1 October 1964; 2861, 1 October 1964; 2862, 1 October 1964; 2865, 
1 March 1968; and 4727, 1 September 1978. 



FM 3-34.331 



Page 

Administrative-Recon Trip 2-9 

Project-Visitation Trip 2-9 

Section III - Project Execution 2-9 

Chapter 3 SURVEY RECON 3-1 

Section I - Recon Fundamentals 3-1 

Recon Requirements 3-1 

Recon-Party Composition 3-2 

Section II - Recon Phases 3-3 

Office Recon 3-3 

Field Recon 3-4 

Recon Reports 3-16 

Chapter 4 DATUMS, GRIDS, AND COORDINATE REFERENCES 4-1 

Datums 4-1 

Grids 4-3 

Coordinate References 4-6 

Chapter 5 CONVENTIONAL SURVEY-DATA COLLECTION 5-1 

Section I - Fundamentals 5-1 

Angle Determination 5-1 

Distance Measurement 5-13 

Electronic Total Stations 5-15 

Section II - Targets 5-16 

Optical-Theodolite Target Set 5-16 

AISI Target Set 5-17 

Target Setup 5-19 

Lighted Target Sets 5-19 

Target and Tribrach Adjustment 5-20 

Signals 5-21 

Section III - AISI 5-24 

Description 5-24 

Components 5-25 

Leveling 5-25 

Quick Check 5-25 

Data Collection 5-27 

File Transfer 5-28 

File Editing 5-28 

Communications 5-29 



FM 3-34.331 

Page 

Instrument Maintenance 5-29 

Section IV - CAD Interface 5-30 

Total-Station Data Collection and Input 5-30 

Plotting 5-31 

Chapter 6 TRAVERSE 6-1 

Starting Control 6-1 

Open Traverse 6-1 

Closed Traverse 6-1 

Fieldwork 6-2 

Traverse Stations 6-3 

Traverse-Party Organization 6-4 

Azimuth Computations 6-4 

Azimuth-Bearing Angle Relationship 6-5 

Coordinate Computations 6-6 

Accuracy and Specifications 6-7 

Chapter 7 DIFFERENTIAL LEVELING 7-1 

Section I - Instruments and Equipment 7-1 

Automatic Levels 7-1 

Digital Levels 7-1 

Optical-Micrometer Levels 7-2 

Leveling Rods and Accessories 7-2 

Instrument Testing and Adjustment 7-2 

Section II - Precise Leveling Procedures 7-5 

Recon 7-5 

DE Determination 7-5 

Field-Party Composition 7-6 

Data Recording 7-6 

C-Factor Determination 7-8 

Center-Wire Adjustment 7-9 

SIF Determination 7-9 

Chapter 8 NAVSTAR GPS 8-1 

Section I - GPS Overview 8-1 

Operating and Tracking Modes 8-1 

System Configuration 8-2 

Broadcast Frequencies and Codes 8-3 

Broadcast Ephemeris Data 8-4 



in 



FM 3-34.331 



Page 
Section II - Absolute Positioning 8-5 

Absolute-Positioning Accuracies 8-5 

Pseudoranging 8-5 

Absolute-Positioning Error Sources 8-6 

User Equivalent Range Error 8-9 

Accuracies 8-9 

Section III - Differential Precise Positioning 8-14 

Code-Pseudorange Tracking 8-14 

Carrier-Phase Tracking 8-15 

Vertical Measurements 8-17 

Differential Error Sources 8-18 

Differential Accuracies 8-18 

Section IV - Precise-Positioning Survey Planning 8-19 

Project-Control Accuracy 8-20 

Network-Design Factors 8-21 

Network Design and Layout 8-28 

GPS-S Techniques 8-31 

Section V - Precise-Positioning Survey Conduct 8-35 

Basic GPS-S Procedures 8-35 

Absolute Positioning 8-36 

Differential Positioning 8-37 

DGPS Carrier-Phase Horizontal-Positioning Surveys 8-39 

Static Surveying 8-40 

Stop-and-Go Kinematic Surveying 8-42 

Kinematic Surveying 8-43 

Pseudokinematic Surveying 8-44 

Rapid-Static Surveying 8-45 

OTF/RTK Surveying 8-45 

Section VI - Precise-Positioning Survey-Data Processing 8-46 

Processing Techniques 8-46 

Baseline Solution by Linear Combination 8-47 

Baseline Solution by Cycle-Ambiguity Recovery 8-49 

Data Processing and Verification 8-49 

Loop-Closure Checks 8-51 

Data Archival 8-54 

Section VII - Precise-Positioning Survey Adjustments 8-54 

GPS Error-Measurement Statistical Terms 8-54 

Adjustment Considerations 8-54 



IV 



FM 3-34.331 

Page 

Survey Accuracy 8-55 

Internal Versus External Accuracy 8-57 

Adjustments 8-58 

Evaluation of Adjustment Results 8-66 

Final-Adjustment Reports 8-68 

Chapter 9 ARTILLERY SURVEYS 9-1 

US Army FA 9-1 

ADA 9-2 

Survey Planning 9-3 

Chapter 10 AIRFIELD-OBSTRUCTION AND NAVAID SURVEYS 10-1 

Airport Obstruction Charts and NAVAID Surveys 10-1 

FAAand FAR Standards 10-2 

Airfield-Data Accuracy Requirements 10-7 

Reporting 10-8 

Chapter 11 REPORTS, BRIEFINGS, AND OPERATION ORDERS 11-1 

Section I - Reports 11-1 

General 11-1 

ISVT Report 11-2 

Recon Report 1 1-3 

Progress Report 1 1-6 

End-of-Project Report 11-6 

Incident Report 1 1-7 

Report Disposition 1 1-8 

Section II - Briefings 11-8 

Impromptu Briefing 1 1-8 

Deliberate Briefing 1 1-8 

Briefing Procedures 11-11 

Section III - Survey SOP and Supporting Annexes 11-13 

Appendix A MENSURAL CONVERSION CHARTS A-1 

Appendix B CONTROL-SURVEY STANDARDS B-1 

Differential Leveling B-1 

Horizontal-Angle Measurement B-3 

Trigonometric Observations B-4 

GPS Techniques B-5 



FM 3-34.331 



Page 

Appendix C BASIC SURVEY COMPUTATIONS C-1 

Computation of a Two-Point Intersection C-1 

Computation of a Grid Traverse and Side Shots C-7 

Computation of a C-Factor C-24 

Computation of a Level Line C-28 

Appendix D SURVEY FORMS D-1 

GLOSSARY Glossary-1 

BIBLIOGRAPHY Bibliography-1 

INDEX lndex-1 



VI 



Preface 

This FM is a guide for military occupational specialty (MOS) 82D (Topographic Surveyor). It 
provides techniques not found in any commercial text concerning the precise determination of 
position, azimuth, or elevation of a point. Additionally, this publication describes and 
standardizes procedures for performing recons, preparing station descriptions, and reporting and 
briefing of survey projects. 

The material in this manual is applicable, without modification, to all geodetic survey projects in 
all environments (prebattle, conventional war [nuclear and nonnuclear], low intensity conflicts, 
and postbattle). The contents comply with Army doctrine and international precision surveying 
practices. This manual does not provide previously published surveying doctrine or theory and 
may be supplemented with commercially available texts or previous editions of technical 
literature. 

Appendix A contains mensural conversion charts. 

The proponent of this publication is HQ, TRADOC. Send comments and recommendations on 
Department of the Army (DA) Form 2028 directly to United States (US) Army Engineer School 
(USAES), Attention: ATSE-DOT-DD, Directorate of Training, 320 Engineer Loop, Suite 336, Fort 
Leonard Wood, Missouri 65473-8929. 

Unless this publication states otherwise, masculine nouns and pronouns do not refer exclusively 
to men. 



VII 



Chapter 1 

Missions, Operations, and Duties 

Surveyors determine horizontal and vertical distances between objects, 
measure angles between lines, determine the direction of lines, and 
establish points of predetermined angular and linear measurements. After 
completing field measurements, surveyors use these measurements to 
compute a final report that is used for positioning by field artillery (FA), 
air-defense artillery (ADA), aviation, intelligence, communications, or 
construction control points. Appendix B summarizes the standards for 
control surveys, Appendix C details the recommended procedures for basic 
survey computations, and Appendix D includes a list of survey forms. 

SURVEY MISSIONS 

1-1. Army topographic surveyors support multiple types of survey missions. 
These missions can be peacetime or wartime oriented. 

SUPPORT DEPLOYABLE WEAPONS SYSTEMS 

1-2. Army topographic surveyors support FA and ADA deployable weapons 
systems by acquiring position and azimuth data as follows: 

• FA. FA is a primary user of precise positioning and orientation 
information in a wartime environment. Topographic-survey support is 
provided to the multiple-launch rocket-system (MLRS) units, the 
corps's general -support (GS) units, and other nondivisional assets in 
the corps area according to FM 6-2. FA requires that topographic 
surveyors provide monumented survey control points (SCPs) 
(horizontal and vertical) and azimuthal references for conventional 
and inertial FA survey teams. FA sometimes requires topographic 
surveyors to augment FA survey sections. 

• ADA. ADA requires positioning and orientation information for ADA 
systems. ADA and FA have an agreement that FA surveyors 
(MOS 82C) will provide direct ADA survey support. 

SUPPORT THE NATIONAL IMAGERY AND MAPPING AGENCY 

1-3. The National Imagery and Mapping Agency's (NIMA's) geodetic survey 
division maintains US Army topographic surveyors as part of their survey 
force structure. These surveyors are involved as team leaders, as team 
members, and in the data-reduction process. In addition, these Army 
personnel are used in areas or situations where Nl MA civilian personnel are 
not authorized (Saudi Arabia, Somalia, and so on). NIMA has the 
responsibility to provide earth-orientation data for the Navigation-Satellite 
Timing and Ranging (NAVSTAR) Global-Positioning System (GPS). NIMA 



Missions, Operations, and Duties 1-1 



FM 3-34.331 



provides correlated World Geodetic System (WGS) 1984 (WGS-84) airfield 
surveys and geographical and aeronautical database information that are 
needed to support the aviation approach requirements. NIMA also determines 
transformation parameters between geodetic systems. I n many areas of the 
world, the transformation parameters are uncertain or unreliable. During 
times of conflict, Army topographic surveyors may be required to collect data 
to enable NIMA to better formulate these transformation parameters. 

SUPPORT THE US ARMY AERONAUTICAL SERVICES AGENCY 

1-4. The US Army Aeronautical Services Agency (USAASA) requires periodic 
airfield and navigational-aid (NAVAID) surveys and airport obstruction 
charts (AOCs) according to Army regulation (AR) 95-2. These surveys are 
extensive field-survey operations that provide aeronautical and other 
information to support a wide range of National Airspace System (NAS) 
activities. AOC surveys provide source information on— 

Position. 

Azimuth. 

Elevation. 

Runways and stopways. 

NAVAIDs. 

Federal Aviation Regulation (FAR), Part 77 (FAR-77) obstructions. 

Aircraft movement and apron areas. 

Prominent airport buildings. 

Selected roads and other traverse ways. 

Cultural and natural features of landmark value. 

Miscellaneous and special request items. 

1-5. The positioning and orientation information for NAVAI Ds is required to 
certify the airfield instrument-landing approaches. AOC surveys also 
establish geodetic control in the airport vicinity, consisting of permanent 
survey marks accurately connected to the National Spatial Reference System 
(NSRS). This control and the NSRS connection ensure accurate relativity 
between surveyed points on the airport and between these points and other 
surveyed points in the NAS, including the navigation satellites. 

SUPPORT THE US AIR FORCE 

1-6. The US Air Force (USAF) requires positioning and orientation data for 
the initialization of Inertial Navigation Systems (I NSs), I NS test pedestals, 
NAVAIDs, and compass roses. The USAF relies on NIMA to satisfy all of its 
positioning and orientation requirements. Army topographic surveyors are 
currently assigned to assist Nl MA in establishing survey control for the 
USAF. 

SUPPORT THE US ARMY INTELLIGENCE AND SIGNAL ELEMENTS 

1-7. The intelligence and signal elements require positioning information for 
remote-operated vehicles, remote sensing-and-i magi ng systems, antenna 
systems' geolocat ion and direction, inertial navigation initialization, situation 
awareness, and combat identification. This information includes the following: 



1-2 Missions, Operations, and Duties 



FM 3-34.331 



Accuracy. The accuracy requirement for intelligence and signal 
elements is similar to the accuracy expressed by FA and ADA. I n 
many cases, intelligence and signal units can use the SCPs 
established for FA and ADA. 

Frequency and timeliness. The number of SCPs and thetimeliness 
are dependent on the battlefield and the mission. 
Distribution. This survey information is distributed to each 
intelligence and signal battalion's operations section, Operations and 
Training Officer (US Army) (S3). Topographic surveyors are 
responsible for notifying the S3 of the various datums within the area 
of operation (AO). I n addition, topographic surveyors provide the S3 
with the necessary parameters and instructions on how to transform 
local coordinates to a predefined common grid (for example, WGS 84). 



SUPPORT J Ol NT-LEVEL MISSIONS 



1-8. During joint-level operations, topographic surveyors may be tasked to 
perform a number of different missions. Topographic surveyors are capable of 
providing support to allied nations for any of the aforementioned defined 
areas. 



SUPPORT OTHER TOPOGRAPHIC MISSIONS 



1-9. These other topographic missions are defined in AR 115-11, FM 5-105, 
unit table(s) of organization and equipment (TOE), and directives from higher 
headquarters (HQ). These missions— 

• Provide precise positioning to support the updating of the MOS 81T 
(Terrain Analyst) database. 

• Support construction surveyors (when projects require real-world 
coordinates). 

• Establish and extend basic control for field surveys. 

• Allow survey data and station description cards to be forwarded to 
N I M A, the organization's survey information center (SI C), and 
collocated terrain-analyst teams (upon request). 



SURVEY OPERATIONS 



1-10. The actual shape of the solid mass of the earth is referred to as the 
topography. A geoid is defined as the surface of the earth's gravity (attraction 
and rotation), which on the average, coincides with the mean sea level (MSL) 
in the open undisturbed ocean. A spheroid (also called an ellipsoid of 
revolution) appears as a figure that is flattened at the poles and bulging at the 
equator. It can be described using a mathematical formula that approximately 
defines a part of the surface of the geoid. However, because of the great 
variations in topography, many different ellipsoids exist. Because the earth's 
surface is irregular and pieces of mathematical computations are unreliable, 
the type of survey conducted depends on the purpose or level of accuracy 
required. 



Missions, Operations, and Duties 1-3 



FM 3-34.331 



SURVEY TYPES 



Plane Survey 



1-11. In plane surveys, all points are referenced to a flat plane with curvature 
wholly or mostly ignored. In geodetic surveys, all established points are 
referenced to the curved surface of a spheroid and, in all computations, the 
effect of curvature is computed. 



1-12. Plane surveys ignore the actual shape of the earth and apply the 
principles of plane geometry and trigonometry. These surveys are treated as if 
the measurements were made on a flat plane, with all lines being straight. 
When the survey area is less than 250 square kilometers and less accuracy is 
needed, curvature can be ignored. Most localized construction projects 
(highway and railroad) and boundary projects use plane surveys. 



Geodetic Survey 



1-13. Geodetic surveys take into account the size and shape of the earth. 
Since the stations in geodetic surveys are routinely spaced over extended 
distances, more precise instruments and techniques are required than for 
plane surveys. All observations are made on the actual curved surface of the 
earth and this curvature is corrected through computations. 



SURVEY METHODS 



Conventional Survey 



GPS Survey 



1-14. Topographic surveyors use theodolites, levels, and distance measuring 
equipment (DM E). The automated integrated survey instrument (Al SI ) 
provides topographic surveyors with the capability to extend control through 
the use of a total station. 



1-15. The NAVSTAR GPS is capable of determining accurate positional, 
velocity, and timing information. The GPS provides positional and 
navigational data to civilian and military communities in the form of two 
positional services. The Standard Positioning Service (SPS) encompasses the 
civilian user and the US Coast Guard (USCG). When using a single GPS 
receiver (absolute positioning), SPS users are denied the high-accuracy, 
instantaneous positioning capability of the GPS. The Precise Positioning 
Service (PPS) consists of military users and authorized representatives. PPS 
users can obtain high-accuracy, instantaneous positioning if the receiver is 
capable of accepting the necessary cryptologic variables. 

1-16. Absolute and differential (relative) positioning methods using the GPS 
provide accurate and timely positional data. The method of choice depends on 
the accuracy required, the equipment available, and the logistical 
requirements. At present, the PPS GPS receiver, which is capable of 
performing relative positioning, is theGPS-survey (GPS-S) differential GPS 
(DGPS). The positioning methods are described as follows: 



1-4 Missions, Operations, and Duties 



FM 3-34.331 



• Absolute positioning. Absolute positioning uses a single GPS 
receiver and does not require known survey control. Absolute 
positions can provide instantaneous (real-time) or postprocessed 
positions. Known survey control is unreliable or nonexistent in 
immature theaters. Topographic surveyors can establish SCPs by 
using absolute positioning. 

• Differential positioning. Differential positioning uses two or more 
GPS receivers. OneGPS receiver (reference receiver) is resident over a 
known SCP. The remaining receivers (remote receivers) are used to 
position points of interest. Differential positioning can be performed in 
real time or through postprocessing. If real-time positioning results 
are required, a communications link that is capable of transmitting 
digital data must be established at the reference- and remote- receiver 
locations. This method supports distances up to 100 kilometers 
between the reference and remote stations. The engineer battalions 
(topographic) within the Army have PPS GPS receivers that are 
capable of real-time and postprocessed differential positioning and 
provide relative accuracy of approximately 1 centimeter. 

1-17. The accuracy of GPS-S is dependent on the user's equipment (precise 
lightweight GPS receiver [PLGR]) and the surveying method employed 
(absolute real-time or differential). Topographic surveyors have standardized 
PPS GPS receivers. These receivers have improved the efficiency and 
productivity of topographic surveyors and have provided the Defense Mapping 
School (DMS) and the USAES a background on the training, operational, and 
research and development requirements that are necessary to successfully 
field the GPS. The new GPS-S provides adequate absolute-positioning results 
and is designed to provide protection in a jamming/spoofing environment. The 
requirement for a PPS GPS receiver that iscapableof performing DGPS when 
using the military's authorized, encrypted pseudorandom noise (PRN) code(Y- 
code) has been met. This receiver satisfies the positional accuracy 
requirements of the Army, the Department of Defense (DOD), and joint-level 
commands. 



SURVEY CLASSIFICATIONS 



1-18. Topographic surveyors are capable of conducting and supporting a wide 
variety of surveys. Surveys are classified as follows: 

Artillery. 

Basic control. 

Satellite. 

Construction. 

Airfield engineering and NAVAID. 

Hydrographic. 

Field classification and inspection. 

Land. 

Inertial. 



Missions, Operations, and Duties 1-5 



FM 3-34.331 



Artillery Surveys 



1-19. Artillery surveys are conducted to determine the relative positions of 
weapons systems to targets. These surveys do not require the accuracy of 
geodetic-surveying techniques despite the relatively large areas and long 
distances. The requirements, methods, and techniques used by military FA 
surveyors aredetailed in FM 6-2 and Chapter 11 of this manual. ADA weapon 
systems require accuracies that are obtainable only from geodetic-surveying 
techniques. 



Basic-Control Surveys 



1-20. Basic-control surveys provide horizontal and/or vertical positions of 
points. Supplementary surveys may originate from and can be adjusted to 
these surveys. The basic-control survey of the U S provides geographic 
positions and plane coordinates of triangulation/traverse stations and the 
elevations or benchmarks (BMs). This information is used as the basis for the 
control of the US national topographic survey; the control of many state, city, 
and private surveys; and hydrographic surveys of coastal waters. The 
techniques and methods used by military geodetic surveyors are discussed in 
this manual. 



Satellite Surveys 



1-21. Satellite surveys determine high-accuracy, three-dimensional (3D) point 
positions from signals received by NAVSTAR GPS satellites. GPS-derived 
positions may be used to provide primary reference-control monument 
locations for engineering and construction projects from which detailed site 
plans, topographic mapping, boundary demarcation, and construction- 
alignment work may be performed using conventional-surveying instruments 
and techniques. 



Construction Surveys 



1-22. Construction surveys provide data for planning and cost estimating. 
This data is essential to locate or layout engineering works and is recorded on 
engineer maps. Plane surveys are normally used for construction projects. The 
methods and techniques used by military construction surveyors aredetailed 
inFM 5-233. 



Airfield-Engineering and NAVAID Surveys 



1-23. Airfield-engineering and NAVAID surveys are used to determine any 
combination of the following: 

The location of obstacles within 10 nautical miles of an airfield center. 

The dimensions of runways and taxiways, the height of flight towers, 

andNAVAIDs. 

The safe approach angles to runways and the minimum, safe glide 

angle. 

The elevation of the barometer on an airfield. 

The positions and azimuths of points designated for I NS checkpoints. 



1-6 Missions, Operations, and Duties 



FM 3-34.331 



The requirements of the Federal Aviation Administration (FAA), 
United States Army Aeronautical Services Agency USAASA, or 
equivalent military activity. 

The information used to assist a military-aircraft crash or disaster 
incident investigation. 



Hydrographic Surveys 



1-24. Hydrographic surveys are made on large bodies of water to determine 
channel depths for navigation and the location of rocks, sandbars, lights, and 
buoys. I n rivers, these surveys are made to support flood-control projects, 
power development, navigation, water supplies, and water storage. 



Field-Classification and Inspection Surveys 



Land Surveys 



1-25. Field-classification and inspection surveys can help to identify features 
not normally revealed using a compiler (for example, political boundary lines, 
names of places, road classifications, and buildings obscured by trees). These 
surveys can also clarify aerial photographs by using comparisons with actual 
ground conditions. 



1-26. Land surveys are used to locate the boundaries and areas of tracts of 
land. These surveys may be done on a city, county, state, national, or 
international level. 



Inertial Surveys 



1-27. I nertial surveys are used to determine relative positions and azimuths. 
The Position and Azimuth Determination System (PADS) is now being used 
extensively to support artillery surveys. 



SURVEY NETWORKS 



1-28. Each survey has a fundamental classification of control points called a 
network. There are several different types of networks. A network of control 
areas usually establishes horizontal and vertical SCPs within a country. 
These areas are all referenced to a single datum and are related in position or 
elevation to each other. Networks are classified as basic, supplementary, and 
auxiliary. All horizontal networks in the US are referenced to the North 
American Datum (NAD) of 1927 (NAD 27) and the NAD of 1983 (NAD 83) 
(NAD 83 and WGS 84 are the same), with coordinates currently being 
published in both. The National Geodetic Vertical Datum of 1929 (NGVD 29) 
and the North American Vertical Datum of 1988 (NAVD 88) are used for 
vertical control points. Within the continental US (CON US), the following 
terms are used: 



Basic Horizontal-Control Networks 



1-29. Basic horizontal -control networks are usually established by f i rst-order 
geodetic-triangulation, traverse, or GPS procedures. The lines of the basic 
network are spaced at intervals of about 96 kilometers throughout a country. 



Missions, Operations, and Duties 1-7 



FM 3-34.331 



Basic Vertical-Control Networks 



1-30. Basic vertical-control networks are established by first-order 
differential leveling along lines spaced from 90 to 160 kilometers apart 
throughout the country. Permanent BMs (PBMs) are spaced at intervals of 
about 3 kilometers on these lines. 



Supplementary Horizontal-Control Network 



1-31. Supplementary horizontal-control networks are usually established by 
second-order survey techniques. These supplementary networks are used to 
fill in the areas between the basic-control lines. Ultimately, either a basic or a 
supplementary network station will be spaced at intervals of about 6 to 16 
kilometers across a country. 



Supplementary Vertical -Control Network 



1-32. Supplementary vertical-control networks are established by second- 
order differential leveling. These lines are run within the basic-control lines to 
provide a planned control-line spacing at intervals of about 10 kilometers. 
PBMs areemplaced at intervals of about 2 kilometers apart on these lines. 



Auxiliary Horizontal-Control Networks 



1-33. Horizontal auxiliary-control networks are usually established by 
second- or third-order survey techniques. They provide localized control to be 
used by surveyors for artillery control, construction-engineering surveys, 
mapping projects, or other positioning requirements. As more states and other 
agencies require geodetic accuracy for boundary and property surveys, they 
will use these networks. 



Auxiliary Vertical-Control Networks 



1-34. Auxiliary vertical-control networks are established by third-order 
differential leveling and are used to provide localized vertical control. They 
are also used to support artillery, construction, and engineering projects. 



SURVEY EQUIPMENT 
Conventional Survey Equipment 



NAVSTAR GPS 



1-35. Topographic surveyors have theodolites, levels, and electronic DME 
(EDME) within their inventory. The A I SI provides topographic surveyors with 
the capability to extend control in a timelier and more efficient manner. The 
AISI is a total station that combines angular, distance, and vertical 
measurements into a single electronic instrument that is designed to digitally 
record and transfer data into a personal computer (PC). 



1-36. The NAVSTAR GPS is capable of determining accurate positional, 
velocity, and timing information. The PPS consists of military users and 
authorized representatives. A PPS user can obtain high-accuracy 
instantaneous positioning if the receiver is capable of accepting the necessary 



1-8 Missions, Operations, and Duties 



FM 3-34.331 



cryptologic variables. When two or more receivers are used, it is called DGPS 
surveying. The error values are determined and removed from the survey 
either by real-time processing or postprocessing of the data. The type of DGPS 
survey used is dependent on accuracy requirements. Therearetwo basictypes 
of DGPS surveys— static and dynamic. 

• Static survey. Static surveying uses a stationary network of 
receivers that collect simultaneous observations over a predetermined 
time interval and yield the best accuracy. 

• Dynamic survey. Dynamic surveying uses one stationary receiver 
and any number of remote or roving receivers. It allows for rapid 
movement and the col lection of data over a large area. When operating 
in the real-time mode, the roving receiver can provide very accurate 
positions almost instantaneously on the battlefield. 



Computer Information Systems 



1-37. Surveying has become a digital science. Modern survey systems work 
with software specifically designed to process field data, perform 
computations, and produce a precise product, whether it be a GPS network, a 
digital database, or a computer-aided design (CAD) and drafting (CADD). 
GPS-S computations require a PC to process large amounts of mathematical 
variables. Efforts should be ongoing to obtain or upgrade to the fastest system 
available. Computer resources are standardized throughout TOE units with 
topographic surveyors. Application (such as databases or word processing) 
and functional (such as adjustment or CAD) software packages have increased 
the efficiency and productivity of topographic surveyors. The SIC collects and 
disseminates the positioning and orientation requirements for such 
organizations as Nl M A, FA, ADA, Armor, and the USAF and maintains a 
digital database capable of archiving, querying, and manipulating survey 
control. Topographic surveyors are equipped with common GPS hardware and 
software and CAD and survey-application software. 

SURVEY-PERSONNEL DUTIES 

1-38. Topographic surveyors supervise and/or conduct surveys to provide 
control data for mapping, artillery, and aviation support and supervise or 
perform topographic or geodetic computations. Duties for MOS 82D (at each 
skill level) are identified below. 

MOS 82D10 

1-39. Skill level 1 surveyors— 

• Record topographic-survey data. 

• Operate and collect data with a GPS, electronic and mechanical 
theodolites, EDM E, and differential-leveling equipment. 

• Perform topographic computations; compute elevations of tidal BMs 
and baselines; and transport, set up, operate, and maintain 
equipment according to written, oral, or visual instructions from 
supervisors. 

• Prepare abstracts of field data for final computations. 



Missions, Operations, and Duties 1-9 



FM 3-34.331 



MOS 82D20 



MOS 82D30 



MOS 82D40 



Assist in the emplacement and recovery of control stations and 

prepare station description cards. 

Compute abstracted survey data for final tabulation. 



1-40. Skill level 2 surveyors- 
Transport, set up, operate, and maintain equipment according to 
written, oral, or visual instructions from supervisors. 
Make field checks to ensure that field measurements meet project 
specifications and classifications. 

Perform observations and compare, standardize, and calibrate survey 
equipment. 

Input field-survey data into CAD programs and process CAD data into 
final products. 

Transfer, process, and adjust GPS data by using survey software and 
PCs. 

Compute and adjust first-, second-, and third-order horizontal- and 
vertical-control surveys. 

Perform preliminary and field computations to verify field 
observations for control surveys and compute preliminary values of 
horizontal and vertical control points. 

Convert grid and geodetic coordinates and transform (in the same 
system) coordinates and azimuths from one zone to adjacent zones. 
Operate and write programs for programmable electronic calculators. 
Operate PCs. 
Direct and control personnel when acting as a survey-party chief. 



1-41. Skill level 3 surveyors— 

• Supervise and direct topographic surveys. 

• Prepare project progress reports and conduct project briefings. 

• Recommend the method of computation and adjustment and the need 
for additional data. 

• Evaluate and verify results of all computations. 

Direct the transportation, setup, operation, and maintenance of 
equipment according to written, oral, or visual instructions. 

• Perform a survey recon (to include picture-point selection) and main 
and secondary survey-station placement and evaluate field data and 
the results obtained. 

• Plan and analyze the collection of traverse, triangulation, leveling, 
and satellite data and isolate computational or field blunders. 

• Supervise CAD survey operations. 



1-42. Skill level 4surveyors- 



1-10 Missions, Operations, and Duties 



FM 3-34.331 



Plan and approve topographic surveys. 

Supervise recon studies and reconnoiter survey sites to determine 
special requirements of obstacles encountered. 
Plan and arrange logistical support for topographic-survey activities. 
Plan and organize work activities. 
Coordinate surveying and computing activities. 
Supervise field-survey activities in support of task and mission 
requirements. 

Determine composition and operational techniques of topographic- 
survey parties. 
Perform quality checks on survey data. 

Collect available charts, maps, control lists, aerial photographs, and 

other topographic data that are necessary to maintain a deployable 

database. 

Disseminate survey data. 

Serve as the technical authority in all survey matters. 



FIELDWORK 



1-43. Topographic surveyors perform most of their operational duties away 
from the parent unit. Topographic surveying involves fieldwork over a project 
area or battlefield. Survey fieldwork consists of making observations and 
measurements; recording data; and returning the data to a computer and/or 
draftsman for computation, compilation, and dissemination. Surveyors must 
overcome many factors that combine to affect working conditions. They must 
be constantly alert to various factors such the following: 

• Weather and terrain. Weather and terrain can adversely affect field 
surveys. The effectiveness of optical and electro-optical instruments 
can be severely reduced by fog, mist, smog, or ground haze. Swamps 
and floodplains under high water can impede leveling operations. 
Signals from the GPS constellation generally require a clear line of 
sight to the sky. U rban and forested areas can mask or deflect the 
direct signal that is needed for accurate measurements. Good recon 
and proper planning can alert the field parties of the best times and 
methods to use. 

• Personnel. The rate of progress often varies in direct proportion to 
the training and experience level of the assigned personnel. The most 
effective method of training personnel is under conditions where their 
actions have real consequence as opposed to mere practice. On-the-job 
training produces a measurable product but frequently results in lost 
work due to correcting mistakes. 

• Equipment. Equipment reliability must be considered when setting 
completion dates. Modern, well-maintained equipment can often 
increase the rate of progress. Older equipment, if properly maintained 
or adjusted, will yield accurate results. Repairing or replacing broken 
instruments or parts will sometimes slow down or stop a field survey. 
Equipment must be calibrated as part of combat checks before the 
survey mission begins. 



Missions, Operations, and Duties 1-11 



FM 3-34.331 



• Purpose. The purpose and the type of survey will determine the 
accuracy requirements. Control networks are established by using 
high-accuracy GPS, triangulation, traverse, or leveling procedures. At 
the other extreme, cuts and fills for a highway have much lower 
standards. I n some surveys, distances to inaccessible points must be 
determined. High-accuracy distance and angle measurements are 
required so that these values, when used in trigonometric formulas, 
will yield acceptable results. This type of survey is directly dependent 
on the clearness of the atmosphere. Observing measurements for a 
single position can be delayed for days while waiting on good weather. 

• Accuracy. Accuracy requirements will dictate the equipment and 
techniques selected. For instance, comparatively rough techniques can 
be used for elevations in site surveys, but control-network leveling 
requires much more precise and expensive equipment and extensive, 
time-consuming techniques. 

• Errors. All measurements contain some amount of error. Errors 
classified as systematic and accidental are the most common 
uncontrollable errors. Besides errors, measurements are susceptible 
to mistakes or blunders that arise from misunderstanding the 
problem, poor judgment, confusion, or carelessness. The overall effect 
of mistakes and blunders can be greatly reduced by following a 
preestablished systematic procedure. This procedure will be 
advantageous in all phases of a survey. 

Progress rates. Rates of progress vary, depending on experience and 
repetition. As skill and confidence increase, so does speed. Proper 
preparation and planning reduce duplication of effort and increase 
efficiency. 

• Enemy. A hostile environment often forces a schedule adjustment. 
Night work requires greater speed, fewer lights, and increased 
security. Adding security forces increases the number of vehicles and 
personnel, which in turn, reduces efficiency and retards even the most 
ambitious time schedule. 

OBSERVATION OF DISTANCES AND DIRECTIONS 

1-44. Topographic surveyors observe distances and/or directions (angles) for 
the following reasons: 

• To establish GPS, triangulation, and traverse stations for basic, 
supplementary, and auxiliary control networks. 

• To establish gun and target positions for artillery batteries. 

• To establish horizontal control to support PADS. 

• To establish point and lines of reference for locating details (such as 
boundary lines, roads, buildings, fences, rivers, bridges, and other 
existing features). 

• To stake out or locate roads, buildings, landing strips, pipelines, and 
other construction projects. 

• To establish lines parallel to, or at right angles to, other lines or to 
determine the area of tracts of land, measure inaccessible distances, 
or extend straight lines beyond obstacles. 



1-12 Missions, Operations, and Duties 



FM 3-34.331 



• To establish picture points for databases. 

• To do any other work that requires 
trigonometric principles. 

OBSERVATION OF DIFFERENCES IN ELEVATIONS 



the use of geometric or 



1-45. Topographic surveyors observe differences in elevation (DEs) for the 
following reasons: 

To establish BMs for basic, supplementary, or auxiliary vertical- 
control networks. 

To determine DEs of terrain along a selected line for plotting projects 
and computi ng grade I i nes. 

To stake out grades, cuts, and fills for earthmoving and other 
construction projects. 

For trigonometric elevations of triangulation and traverse stations for 
control networks and mapping projects. 
To establish gun and target positions for FA batteries. 



RECORDING OF FIELD NOTES 



Quality 



1-46. Topographic surveyors record field notes to provide a permanent record 
of thefieldwork. These notes may take any of the following formats: 

Field-recording booklets. 

Single-sheet recording forms. 

Digital disks or devices for automated data recording. 

Land-survey plans. 

Property plans. 

Recovery and station description cards. 

Control diagrams showing the relative location, method, and type of 

control established and/or recovered. 

Even the best field survey is of little value if the field notes are not complete 
and clear. The field notes are the only records that are left after the survey 
party leaves the field site. Surveyors' notes must contain a complete record of 
all measurements or observations made during the survey. When necessary, 
sketches, diagrams, and narration should be made to clarify notes. Write 
overs, erasures, or use of correction tape or fluid are strictly forbidden. These 
actions, when prohibited by the unit's survey standing operating procedure 
(SOP), are cause for punishment under the Uniform Code of Military J ustice. 
Recording errors are to be lined out and initialed by the recorder and the 
corrected reading entered on the recording form. 



1-47. Good field notes share the following qualities: 

• Neatness. The lettering should conform to the gothic style portrayed 
in FM 5-553. All entries should be formatted according to unit SOPs. 

• Legibility. Only one interpretation should be possible. Decimal 
points and commas must be clear and distinct. 



Missions, Operations, and Duties 1-13 



FM 3-34.331 



Organization 



Format 



Completeness. All entries should be complete, and all resolved data 
must be finished according to unit SOPs. All entries must— 

Bedoneon the correct forms and entirely in thefield. Never record 
notes on scrap paper and then transcribe them to a field-recording 
form. If performing an underground survey, use a covered 
clipboard to protect the notes. 

Accurately describe the field experience. Sketches, diagrams, and 
notes will reduce or eliminate questions. 



1-48. Survey notes are usually kept in a field notebook, on individual 
recording forms, or in an automated data collector. Loose-leaf sheets should be 
numbered serially toensurethat all sheets are kept and turned in. Regardless 
of the format used, include— 

• The instructions for the return of the notes or cassette tapes (specify 
any special-handling requirements) in case they are lost. Usually, 
they should be returned to the commander of the particular unit. 

• An index of the field notes and a cross-reference to additional books or 
binders. 

• A list of party personnel and their duties and the project's beginning 
and ending dates. 

• A list of instruments used (include types, serial numbers, calibration 
dates, constant values, and dates used). 

• A generalized sketch and description of the project. 

• The actual survey notes on each page that contain data. Fill out the 
heading and include the following information: 

The station names (include the establishing agency and date). 
The survey date. 

The names and survey duties of personnel (for example, 

instrument operator or note keeper). 

The instruments used (includetheserial numbers). 

Weather data. 

The actual observed data (include all required reductions). 

Pertinent notes, as required. 

The observer's initials at the bottom right corner of the recording 

form (indicating that the observer has checked all entries and 

ensures that they are correct). 



1-49. Recording of field notes takes three general forms— tabulations, 
sketches, and descriptions. 

• Tabulations. Numerical data is recorded in columns following a 
prescribed format, depending on the type of operation, the instrument 
used, and the specifications for the type of survey. 

• Sketches. Sketches add much to the clarity of field notes and should 
be used liberally. They may be drawn to scale (as in plane-table 



1-14 Missions, Operations, and Duties 



FM 3-34.331 



surveys), or they can be drawn to an approximate scale (as in control 
cards). If needed, use an exaggerated scale to show detail. 
Measurements should be added directly on the sketch or keyed in 
some way to avoid confusion. Sketches require the same quality as 
other field notes. 

• Descriptions. Tabulations with or without sketches can also be 
supplemented with narrative descriptions. The description may 
consist of a few words, or it may be very detailed. Survey notes become 
a part of historic records, so a brief description entered at the time of 
the survey may be important and helpful in the future. 

1-50. Abbreviations and Symbols. Standard abbreviations, signs, and 
symbols should be used in all survey notes and must be consistent with 
guidelines in such publications as AR 310-50 and FMs 21-31 and 101-5-1. 
Spell out words if there is any doubt about the meaning or interpretation of a 
symbol or abbreviation. 

1-51. Corrections. Field notes are considered legal documents and can be 
used in court proceedings. As such, no erasures or write overs are permitted. 
No position will be voided or rejected in the field, except in the case of 
disturbing the instrument or target or observing the wrong target. I n either 
case, the position should be reobserved and the location of the reobserved data 
should be noted in the remarks section. Follow these rules for making 
corrections: 

• No erasures. All fieldwork will be done in black or blue-black ink 
(with no erasures) that is suitable for photocopying. The only 
exception is the field sheet of a plane-table survey. 

• No write overs. Field notes show what happened in the field. If a 
number is changed, make a single slanted line through the incorrect 
number. The individual making the corrections inserts the correct 
number directly above or next to the corrected value, creating the new 
entry and i niti al i ng the change. A note wi 1 1 be entered i n the remarks 
column stating why the number was changed. 



OFFICE WORK 



COMPUTING 



1-52. Surveying procedures also consist of converting the field measurements 
into a more usable form. Usually, the conversions or computations are 
required immediately to continue the fieldwork. At other times, they must be 
held until a series of field measurements is completed. This is called office 
work even though some of the operations may be performed in the field during 
lapses between measurements. Some office work requires the use of special 
equipment (calculators, PCs, or drafting equipment) or extensive references 
and working areas. During survey operations, many field measurements 
require some form of arithmetical computation. For example, adding or 
subtracting DEs to determine the height of instrument (H I ) or elevation 
during leveling or checking angles to see that the allowable error (AE) is not 
exceeded. 



1-53. Office computing converts distances, angles, GPS measurements, and 
rod readings into a more usable form or adjusts a position of some point or 



Missions, Operations, and Duties 1-15 



FM 3-34.331 



ADj U STING 



mark from which other measurements can be made. This process involves the 
computation of— 

• Distances. The desired result is the horizontal distance between two 
points. I n electronic distance measurement (EDM ), the distance is 
usually on a slope and has to be corrected for temperature and 
barometric pressure and then reduced to the correct horizontal 
distance. 

• Azimuths and bearings. In many operations, the observed angles 
are converted into directions of a line from north (azimuths) or north- 
south (bearings). 

• Relative positions. The distance and direction of a line between two 
points determine the position of one point relative tothe other point. If 
the direction is given as an azimuth bearing, a trigonometric formula 
(using the sine or cosine of the angle multiplied by the distance) can be 
used to determi ne a coordi nate difference between the two poi nts. 



1-54. Some survey techniques are not complete until one or more of the 
following adjustments are performed. Adjusting is the determination and 
application of corrections to data. Adjusting provides a means of dealing with 
the random errors in a survey network and causes the data to be consistent 
within itself and to a given set of references. Small errors that are not 
apparent during individual measurements can accumulate to a sizable 
amount. In a linear adjustment, for example, assume that 100 measurements 
were made to the nearest unit and required determining which unit mark is 
closer to the actual measurement. Adjusting the result requires reducing each 
measurement by the product that results from dividing the error by the 
number of measurements. Since the measurements were only read to the 
nearest unit, a single adjustment would not be measurable at any point and 
the adjusted result would be correct. Some of the more precise surveys require 
least-square adjustments. 

• GPS network and least-square adjustment. A least-square 
adjustment is the basis for correcting GPS (and traverse) networks 
that use automation to compute solutions in geometry and produce 
geodetic accuracy. A least-square adjustment in a survey network 
allows for the computation of a single solution for each station and 
minimizes the corrections made to the field observations. A least- 
square adjustment uses probability in determining the values for 
particular unknowns, independently weighs all field observations, 
highlights large errors and blunders that were overlooked before 
adjustment, and generates information for analysis after the 
adjustment (including estimates of the precision of its solutions). 

• Traverse. Traverse is the measurement of lengths and the 
determination of directions of a series of lines between known points 
that establishes the coordinates of the intermediate points. When 
computed, the accumulated closing error shows up as a position 
displacement of a known point. The displacement is corrected and 
distributed among the intermediate (traverse) points. 



1-16 Missions, Operations, and Duties 



FM 3-34.331 



Elevation. Depending on the purpose, the elevations on some level 
lines are computed as the measurements are taken. When the line is 
closed, the DE between the measured and the known elevation is 
adjusted over all the stations in the line. In higher-order leveling, only 
the DEs are recorded during the measuring and all adjusting is done 
at the completion of the line. The error is then distributed among the 
various sections of the line. 



ESTABLISHING RECORDS 



CHECKING 



1-55. Office computations reduce the field notes to a tabular or graphic form. 
They become a permanent record and are stored for further use or subsequent 
operations. Many standardized forms are available and should be used. As 
long as the sheets are clearly identified and bound as a set, they are 
acceptable. Normally, all field notes should be abstracted and filed separately. 
The abstracts should be bound along with all computing forms into a single 
binder or folder and maintained on file for further reference. All pages should 
have the name and date of the person performing the work and at least one 
person who verified that page. Do not dispose of or destroy any of these 
records. 



1-56. Surveying involves a series of checks. The field notes should be checked 
by the observer, the recorder, and the party chief before they are turned in for 
office work. Before computing, the assigned person should check the notes 
again. Most mathematical problems can be solved by more than one method. 
In checking a set of computations, it may be desirable to use a method that 
differs from the original computation method. An inverse solution may be 
used, starting with the computed values and solving for the field data or a 
graphic solution. Each step that cannot be checked by any other means must 
be checked by a totally independent recomputation by another individual. Any 
errors or mistakes that are found must be resolved and rechecked before the 
computation is accepted. 



SURVEY COMMUNICATION 



VOICE 



1-57. Survey-party members may find themselves separated. The ability to 
communicate with each other may mean the difference between successfully 
completing a section of work or not. Even at relatively short distances (as in 
site surveys or leveling operations), background noises can obscure direct 
voice contact. At longer distances, such as in EDM or direction-measurement 
operations, effective direct voice contact is impossible. Therefore, some other 
type of communication is required. 



1-58. On long lines, where hand signals are impossible, a radio must be used. 
Each theater of operations or Army command has published communications- 
electronics operation instructions (CEOI) that units must follow. Only 
frequencies obtained through the local signal officer may be used. All 
personnel must be familiar with the CEOI and the unit's communications 



Missions, Operations, and Duties 1-17 



FM 3-34.331 



DIGITAL 



SOP before using a radio. All radio communications must be kept as short and 
secure as possible. 

1-59. Over shorter distances, during all types of site surveys, the Al SI 
provides one-way voice communication. Two-way communication is preferred 
for short distances. Most units have some type of hand-held radios, although 
they are not TOE equipment. These radios should be able to communicate up 
to 5 kilometers and should not be limited to line of sight only. Portability, ease 
of operation, and frequency programmability should be considered when 
procuring this type of communication equipment. Military hand-held radios 
are readily available in most military communities. 

1-60. TOE changes are replacing frequency modulated (FM) radios with 
Single-Channel Ground-to-Air Radio Systems (SI NCGARSs). The need to 
communicate across large distances is increasing in frequency. GPS-Ss are 
conducted at distances of up to 25 kilometers and depend upon 
synchronization between receivers during data collection. Any disruption from 
a singlestation in a GPS network can result in a total loss of effort. 



1-61. The primary focus of survey operations during wartime is to operate 
quickly over large distances. This requires the ability to transmit data 
digitally over the battlefield. The type of data will be largely or entirely GPS 
data. I n order for a survey team to provide accurate positions where needed 
and in a timely manner, they need to operate in real time without having to 
process out the error code embedded in a GPS signal. The process of real-time 
GPS surveying begins with a base-station receiver that broadcasts corrections 
to the signals emanating from the GPS satellites. Army surveyors have the 
following two means of transmitting this data: 

• Radio modem. Surveyors have a radio modem that is designed 
primarily for broadcasting DGPS corrections or raw GPS data from a 
survey base station to one or more roving receivers for real-time 
differential or kinematic (RTK) surveying. These radio modems 
require line of sight between each radio modem. They can beset up in 
a series of repeating stations that extend across the survey area. This 
system is effective only over a small, local area. 

• SINGARS. The primary system for data transmission over the 
distances required on the battlefield is SINCGARS. GPS-S is designed 
to transmit encrypted GPS data over SINCGARS. Any user that can 
receive the data will have a real-time correction to the broadcast GPS 
signal. This gives topographic surveyors the operational capability to 
perform the mission under circumstances where GPS signals are 
dithered or spoofed on the battlefield. A GPS signal can be 
retransmitted over a communication network to multiple users, which 
extends the range and capability of survey operations. 



MISCELLANEOUS 



1-62. M irrors and lights can also be used for communication. A signal mirror 
can use the sun as a light source and is a fairly accurate sighting device. 
Morse code or other prearranged signals can be used to effectively 



1-18 Missions, Operations, and Duties 



FM 3-34.331 



communicate during the day. At night, the same signals can be used with a 
light. 



Missions, Operations, and Duties 1-19 



Chapter 2 

Project Planning 

Survey operations, whether under combat conditions or not, are like any 
other military operation and must be carefully planned. Enthusiasm, 
technical proficiency, and dedication do not make up for poor planning. All 
plans must be dynamic in nature and must be constantly evaluated and 
updated. This chapter addresses project planning, primarily from a 
logistics and administrative standpoint. Most of the information contained 
in this chapter is concerned with prebattle operations. Some technical 
planning will be addressed, but only as it impacts on logistics and 
administrative support. Project planning can be divided into three phases: 
evaluation and scheduling, information-gathering trips, and project 
execution. 



SECTION I - EVALUATION AND SCHEDULING 



2-1. Evaluation and scheduling includes the initial project evaluation, 
determination of the project requirements, assessment of the unit's ability to 
accomplish the project, determination of a preliminary plan and milestones, 
and coordination of the necessary administrative and logistical support. After 
receipt of a project directive, project planning begins. This preliminary 
planning involves evaluating the directive, assessing the unit's capability, and 
determining a preliminary schedule of events. It is important that all 
estimates, including time and funds, be labeled as preliminary for all reports 
or briefings. Many survey missions are in areas where government lodging 
and meals are unavailable or impracticable. The customer must be made 
aware of the scope and pace of survey operations and what the impact may be 
if operations are restricted to a set schedule. This must be done to provide the 
customer, supported units, or higher HQ with an accurate picture of the 
extent and cost of a project. 

PROJ ECT REQUIREMENTS 

2-2. The first step in project planning involves evaluating the requirements 
as stated in the project directive. In many instances, requests will come from 
offices or units that have no real knowledge of survey requirements. The 
support request must be carefully evaluated toensurethat what the customer 
has ordered is, in fact, what the customer needs. This evaluation is usually 
done by the survey noncommissioned officer in charge (NCOIC). Generally, 
the project directive can be classified in one of the following three cases of 
requirement versus need: 

• The customer has requested work that is more accurate than is 
needed. 



Project Planning 2-1 



FM 3-34.331 



• The customer has requested work that is less accurate than is needed. 

• The customer has requested work that matches the need. 

2-3. I n the first case, the customer is typically not survey-oriented and only 
sees the orders and classes of accuracy as words and numbers on a page. The 
customer does not understand the differences and the cost implications of 
each. Generally, a telephonic explanation of the differences in the orders of 
accuracy will resolve most potential conflicts. I n those cases where the 
customer cannot be swayed from an erroneous perception of the orders of 
accuracy, an explanation of the cost differences will generally change the 
customer's mind. If the customer remains adamant about the request, start 
planning to accomplish the original request. 

2-4. I n the second case, the customer must be contacted and the differences in 
theorders of accuracy explained. Since funding costs usually go up or down in 
direct proportion totheorder or class of accuracy, it may be difficult tochange 
the customer's attitude about the request. If the customer cannot be swayed, 
start planning to accomplish the original request. 

NOTE: Careful documentation of all contacts and conversations with the customer 
should be kept, especially in the first two instances. At some future date, the customer 
may realize that the survey unit gave good advice and may wish to change the initial 
request. If the recommendations for change are not documented accurately, the unit 
may be liable to correct a project without additional funding. 

2-5. In the third case, planning can begin immediately. This is usually the 
case when dealing with other military units that are routine survey users. 

UNIT CAPABILITIES 

2-6. Assessing the unit's ability to conduct any type of survey is perhaps one 
of the most difficult tasks. Fortunately, many mechanisms exist to assist in 
this evaluation. The single best indicators are the commander's and the 
survey-section leader's personal familiarity with the soldiers. Since this is not 
always accurate, a number of systems have been established to help in this 
evaluation. Two of these systems are as follows: 

• Army Training and Evaluation Program (ARTEP). ARTEPs 
contain mission training plans (MTPs), battle drills, and evaluation 
guides for assessing a unit's ability to conduct various team tasks. 

• Unit files. These files contain information on a unit's past 
performance on similar projects. They contain the names of personnel 
who conducted the project and the duration time. Any previous 
problems are listed and explained in great detail. 

2-7. This information can prove to be very valuable, notonlyfor assessing the 
unit's ability to conduct the project, but also in planning the project as a 
whole. A listing of the unit's training deficiencies can be generated. The 
survey-section leader can develop a training program to address any 
shortcomings. This program has to be designed around the project milestones. 
The tendency to assign the most qualified personnel should be avoided. 
Usually, a mix of highly qualified and entry-level soldiers should be assigned 
to any project to ensure that new people get the experience they need. 



2-2 Project Planning 



FM 3-34.331 



ACCURACY CONSTRAINTS 



2-8. The Federal Geodetic Control Committee (FGCC) established the 
Standards and Specifications for Geodetic Control Networks (SSGCN). These 
standards defi ne the orders of accuracy for geodetic work conducted in the US. 
These SSGCN are used to ensure uniformity of all work conducted to support 
and extend the US National Control Network. The Army, through the US 
Army Corps of Engineers (USACE), is a member of the FGCC and has agreed 
to comply with the SSGCN. All Army survey activities conducted within the 
US should be in compliance with these standards. 

2-9. When possible, surveys in other nations should also comply. Due to 
military necessity, there will be occasions when compliance is not possible due 
to mission requirements. Some of these situations may involvethe following: 

• Projects conducted in a time of war. 

• Projects conducted as training exercises designed as realistic war- 
training exercises. 

• Projects not intended for inclusion in the US National Control 
Network. 

• Projects conducted to support consumer requests that are specifically 
exempt. 

2-10. When feasible, all field activities should conform totheSSGCN. At some 
later date, it may be determined that any given project should have been 
included in the US National Control Network. If thefieldwork was in total 
compliance, only the computations will need to be refined. 



MILESTONES 



2-11. Milestones are developed for estimating project duration and cost and 
for managing personnel and resources. Milestones generally take the form of a 
timeline, with the events noted as they should occur. A timeline allows a 
commander or a customer to see, at a glance, how a project is proceeding. This 
manual gives general tips on the development of timelines for all types of 
survey activities. Under combat conditions, it may not be feasible to develop 
precise timelines. The flow of a battle may dictate dramatic changes to 
milestones, and most work will have to be accomplished with a very short 
suspense. In these situations, developing a timeline may be time consuming 
and counterproductive. Under normal prebattle operations, it is feasible and 
advisable to develop milestones. Care should be taken to ensure that the 
resulting timeline is not overly ambitious. 

2-12. There are a number of variables associated with any timeline. These 
include, but are not limited to, the following: 

Availability and type of equipment. 
Experience of personnel. 
Terrain, vegetation, and weather. 
Extent or area of project. 
Priority of other projects. 
Enemy or adversary intervention. 



Project Planning 2-3 



FM 3-34.331 



Table 2-1 shows typical rates of progress for various types of survey 
operations. These are only rule-of-thumb estimates. Each unit must develop 
its own rates-of-progress table based on the equipment and the level of 
expertise of assigned personnel. 

Table 2-1. Typical Rates of Progress for Third-Order Surveys Using One Survey Squad 



Basic 
Figure 


Survey Method 


Average Distance 
per Setup 


Hours per Setup 

by Average 

Distance 


Daily Progress 
(10-Hour Day) 


Nonlinear 


GPS 


Static 


100 km 


4.0 


200 km 


50 km 


3.0 


150 km 


10 km 


2.1 


40 km 


Kinematic/RTK 


25.0 km 


2.00 


NA 


1.0 km 


0.50 


NA 


0.1 km 


0.10 


NA 


Linear 


Traverse 


5.0 km 


1.25 


40.0 km 


2.0 km 


0.75 


25.0 km 


1.0 km 


0.50 


20.0 km 


Leveling (differential, 
3-wire, loop) 


200.0 m 


Minutes per setup 


6.0 km 


150.0 m 


4.5 km 


100.0 m 


3.0 km 


NOTES: 

1. Times are subject to delay due to the weather, the road conditions, or the tactical situation. 

2. The survey squad consists of seven personnel. 

3. GPS sessions are using four receivers per session. 

4. The daily progress for RTK surveying is dependent on a network of repeater stations to transmit the 
signal corrections between the base station and the roving receivers. 

5. GPS-network coverage areas depend on the network geometry and the availability of suitable terrain 
for each setup. 



2-13. Project schedules can be established using several different approaches. 
The two most common approaches are to establish the schedule based on a 
firm start or end date. The procedures are similar in both cases, with the 
following differences: 

• If the start date has been firmly established, then the project is laid 
out from beginning to end with each event occurring as it will happen. 

• If theend date has been established, then the project must be planned 
in reverse. That is, events that occur last must be programmed from 
theend of the project backward until a start time is established. 

2-14. I n all cases, schedules must be realistic but not overly ambitious. Delays 
due to weather, equipment, personnel shortcomings, or any other problems 
must be built into the schedule. In most cases, it is better to estimate a longer 
duration time and finish early than to underestimate and miss a scheduled 
end date. 



2-4 Project Planning 



FM 3-34.331 



ADMINISTRATIVE SUPPORT 



2-15. Administrative support is normally concerned with documentation, both 
technical and nontechnical. Technical documentation usually includes typing 
reports, tabulating and preparing technical data, or preparing briefing 
materials. The survey team, with limited help from clerical personnel, often 
accomplish these technical administrative actions. Nontechnical 
documentation usually involves personnel actions and is performed by 
specialists in the Personnel and Administration Center (PAC), the Adjutant 
General (AG) Office, or the finance and accounting office (FAO). This portion 
covers general guidance about what should be accomplished and when, 
primarily with peacetime operations conducted elsewhere than at the unit's 
installation. Wartime requirements are addressed in various SOPs of theunit, 
parent unit, and major Army commands (MACOMs). 



PRIOR TO DEPLOYMENT 



2-16. Before a survey unit deploys to another installation or area, a number of 
administrative actions should be accomplished. All routine personnel actions 
for survey-party members should be accomplished to ensure that there will be 
minimal actions while deployed. All soldiers should make sure that their pay 
portions, allotments, insurance statements, and other financial requirements 
are updated. Other actions that may be required are powers of attorney and 
routine medical checks. If a long duration time is anticipated, all personnel 
should schedule a records review, to include promotion packets, personnel and 
finance records, and emergency data cards. 

2-17. After all these actions have been completed, there will theoretically be 
no need for nontechnical administrative support. I n reality, new actions will 
be required from time to time. Therefore, the party chief should make 
arrangements for handling any actions that may be required during the 
project. The local installation PAC or AG should provide this information. 
Depending on the nature of the required action, the party chief may be able to 
submit the paperwork through the mail. If these actions cannot be done 
through the mail or telephonically, a visit tothe AG at the project installation 
or the nearest military facility may be required. 



DURING A PROJ ECT 



2-18. There will betimes when a party chief or an individual is not able to 
complete a required action. The home installation should provide guidance to 
the party chief on how to address these problems. If the project is being 
conducted on a military installation, the party chief should check in with the 
local AG upon arrival, before any problems are encountered. Contact with the 
AG at the project installation should be made during the recon phase and a 
point of contact (POC) established. This will alert the AG that the survey unit 
is in the area, and the AG will usually give any assistance they can. 

2-19. As is often the case, the project may be in an area other than on a 
military reservation. In the US, there will usually be a military representative 
who can assist. It may be possible to arrange for limited support from a local 
office of the Army Recruiting Command, the Army Reserve, or the Army 
National Guard. Regardless of the source, contact should be established before 



Project Planning 2-5 



FM 3-34.331 



assistance is needed. Technical administrative support will usually be 
nonexistent and is the responsibility of the survey team. 



AFTERAPROJ ECT 



2-20. Nontechnical administrative support after project completion is the 
same as prior to deployment. The local PAC, AG, and FAO will handle these 
actions. These actions include filing travel vouchers, initiating new personnel 
actions, and reviewing personnel and finance records. The parent unit will be 
able to assist with technical administrative support, which normally involves 
finalizing reports and information. 



LOGISTICS SUPPORT 



2-21. This segment gives general guidance on the types of logistics 
arrangements and planning that should be accomplished. M any of these 
topics are covered in very general terms. The numerous requirements of the 
various MACOMs and GS units prohibit this segment from being all- 
encompassing. 



MOVEMENT PREPARATION 



2-22. Moving a unit of any size takes careful and thorough planning. Much of 
the specific information concerning preparation for moving a survey section or 
unit will be contained in the unit's or the parent organization's SOP. It is 
imperative that all equipment and personnel move as cohesively as possible. 
Movement plans should be developed well in advance of any anticipated 
moves and should cover all contingencies. They should address moving 
individual elements and/or the entire unit. Most of the requirements for 
movement are described in FM 55-10, which is a concise reference manual and 
should be available when preparing any movement plans. The information in 
this FM is applicable to most wartime and peacetime situations. I n some 
cases, a MACOM will draft supplemental material. 



COMMUNICATIONS 



2-23. One of the most important and often overlooked aspects of any 
successful operation is communication. During movement (regardless of the 
mode of transportation), the unit will normally be dispersed in convoys. 
During field-survey procedures, thefield teams will be located throughout the 
corps area. It is imperative that the elements of the unit have the ability to 
communicate with the command and control section. 

2-24. Planning for communication support requires the same careful 
attention to detail as any other aspect. Depending on the nature of the 
operation, a determination must be made of how much and what type of 
communication equipment will be required. Normally, there will be a mix of 
landlines, portable radios, and cellular phones. After the number of devices is 
established, the unit must determine how much of its own equipment is 
available. If a unit does not have adequate equipment, it should arrange for 
support from the customer or another organization. This is often a very 
satisfactory solution if it is possible. Another solution is the local purchase of 
hand-held radios. This will probably require a check with the local 



2-6 Project Planning 



FM 3-34.331 



communications center to ensure that there are no frequency conflicts as a 
result of nonstandard communications equipment. However, the unit will 
often have to operate within its own equipment limitations. In this case, it will 
be necessary to reevaluate the planned communications network and 
eliminate some nice-to-have elements. 

2-25. One of the best means of communication is the standard military radio 
that is available in all units. These devices give instant access to all users. 
However, there are a number of problems associated with these radios, to 
include the foil owing major problem areas: 

• Lack of user adherence to approved radio procedures. 

• Potential enemy exploitation of nonsecure communications (such as 
obtaining intelligence information, deception, radio direction finding, 
or jamming). 

• Lack of batteries and poor equipment maintenance. 

• Atmospheric conditions that render the radios inoperative. 

• Limited range of single receivers without radio-relay equipment. 

2-26. The first two problem areas are directly related, and the solutions are 
similar. All units have a CEOI that provides frequency and call-sign 
allocations as well as security measures. Strict adherence to these procedures 
is mandatory. All personnel and radio/telephone operators (RTOs) must be 
trained in the proper procedures to ensure the denial of intelligence 
information to the enemy. This will also help prevent other exploitation 
procedures that any adversary may employ. 

2-27. The lack of batteries and equipment-maintenance problems must be 
addressed before the equipment is used. Proper maintenance on all equipment 
can eliminate most problems. The entire communications system should be 
checked occasionally to ensure that it is functioning as designed. Batteries 
should be stored in an approved fashion and checked and replaced as needed. 

2-28. Atmospheric conditions are a major problem and there are only limited 
solutions. It may be necessary to establish landline communications. If this is 
the best solution, a series of communications checkpoints should be developed 
along travel routes and throughout the AO. This system is often cumbersome, 
particularly if a move is over great distances or through undeveloped areas. 
The establishment of radio relays will sometimes overcome these difficulties. 
In a combat environment, it may be possible to contact the communications 
officer in the corps and arrange for radio-repeater access. 

2-29. After resolving all problems, the only aspect remaining is the use of the 
equipment that has been selected. Following proper radio procedures (as 
specified in the CEOI) and communications-security procedures are very 
important. 



MATERIAL SUPPORT 



2-30. Specific details on how to procure required materials or material 
support is generally found in unit SOPs. The intention of this manual is to 
emphasize the importance of making advance arrangements for these 
resources. As part of the planning process, an estimate of the time and 
materials required must be developed. This estimate is based on past 



Project Planning 2-7 



FM 3-34.331 



experience with similar projects and the known requirements of the present 
project. These requirements should be developed without regard to the cost or 
the difficulty of procurement. Determine what is needed and then figure out 
how to get it. Normally, most of the material support is the responsibility of 
the customer. However, this is not always true. Inability of the customer to 
provide material support should be clearly documented in the reports from 
information-gathering trips. I n particular, the initial site-visitation trip 
(ISVT) and the administrative-recon trip should result in a specific POC for 
acquiring necessary materials. The unit should acquire technical supplies 
through normal supply channels. 



SECTION II - INFORMATION-GATHERING TRIPS 



2-31. I nformation-gathering trips are used to gather information on the 
conduct of the project and for progress evaluation. The information gathered 
will be logistical, administrative, or technical and is used to refine project 
plans and milestones. The following paragraphs describe information- 
gathering trips as they apply to normal prebattle operations. I n some 
instances, these trips can be consolidated or eliminated. The overall need for 
the various described trips will depend on a number of variables, including— 

• The unit's familiarity with the area concerned. 

• The amount of information already available concerning the project or 
the supported unit. 

• The anticipated duration of the project. 

• The amount of problems encountered by the unit. 

INITIAL SITE-VISITATION TRIP 

2-32. The ISVT is basically a fact-finding mission that is normally conducted 
by the survey-section leader and the project party chief. The primary function 
of this trip is to gather information that will be used to plan the project and to 
establish POCsfor the various support functions. 

2-33. All project directives will identify an overall POC. This individual or 
office is normally concerned with the results of the project and may not be able 
to provide specific types of assistance that will be required. Often, the overall 
POC will be able to assist in establishing a POC for administrative and 
logistics requirements. 

2-34. The types of support that must be arranged before any field activity 
include equipment maintenance; medical and dental care; personnel actions; 
supply, lodging, mess, and mail services; and personnel. These arrangements 
must be geared to meet the specific needs of the recon party and to support the 
general needs of the project-execution party. 

2-35. For successful completion of the recon phase, all arrangements with 
respect to care of personnel and equipment must be made during the I SVT. 
Careful records should be maintained and memorandums of agreement 
(MOAs) should be drafted as required. Chapter 11 identifies the 
documentation required as a result of the I SVT. 



2-8 Project Planning 



FM 3-34.331 



ADMINISTRATIVE -RECON TRIP 



2-36. The purpose of the administrative-recon trip is to finalize arrangements 
for the project and to plan the specifics of thefieldwork. Chapter 3 discusses 
how to conduct a survey recon. During the recon, it is imperative that all 
arrangements made during the ISVT be checked to ensure that they are 
correct and viable. There may be a delay between the recon and the project 
execution that causes some previously established POC to change. If this 
occurs, a replacement POC must be established. Any unanticipated event that 
occurs should be carefully documented. Chapter 11 identifies the 
documentation required as a result of the recon trip. 



PROJ ECT-VISITATION TRIP 



2-37. The survey-section leader or a command representative will generally 
conduct the project-visitation trip, which has a twofold purpose. The first is to 
check on the progress of the project, which is the responsibility of the survey- 
section leader. Any recurring technical problems will be discussed at length 
and resolved in such a manner as to preclude recurrences. If problems have 
been occurring before a visitation trip, contact with the parent unit should 
have been made previously. Technical difficulties that need resolution should 
not be left unresolved until a scheduled project-visitation trip. The second 
function is to check on the health, the welfare, and the morale of the troops. 1 1 
is imperative that the commander knows how the troops are doing with 
respect to the job and as individuals. If numerous technical problems have 
been occurring, it is possible that some personal problems are being 
overlooked. The project visitation can often resolve these problems before they 
become major limiting factors on the project execution. A trip report should be 
completed and included in the final project folder for historical purposes. 



SECTION III - PROJECT EXECUTION 



2-38. Project execution is the actual conduct of the project and putting the 
project plans into effect. Unexpected or unusual circumstances may require 
plan modifications. If all planning has been done correctly, the survey team 
should arrive and be able to go straight to work without delays. As problems 
occur, the POC should be contacted and the problems resolved as 
expeditiously as possible. Specific details on project execution are covered in 
the following chapters concerning each survey activity. Chapter 3 identifies 
the documentation required for all phases of project planning and execution. 



Project Planning 2-9 



Chapter 3 

Survey Recon 

The recon party must consider special factors, as determined by the 
objective of the survey, and the methods, techniques, and equipment that 
will be employed. This chapter discusses general recon considerations. 
Survey methods and techniques are discussed in thefollowing chapters. 



SECTION I - RECON FUNDAMENTALS 



RECON REQUIREMENTS 



GPS 



3-1. A proper survey recon incl tides- 
Gathering all existing survey data about the target area. 
Testing and determining the usability and visibility of existing 
stations. 

Selecting sites for the main and supplemental stations. 
Determining the monumentation requirements. 
Collecting terrain and climatic information. 
Arranging for access to private or government property. 
Checking on the availability of lodging, mess, medical, maintenance, 
and other required support. 



3-2. I nterreceiver visibility is not required for GPS surveying. Stations can be 
set according to network-design principles rather than traversing around 
buildings or mountains. The only requirement for receiving GPS signals is a 
clear view of the sky. Sources of electro-magnetic interference and tall 
buildings should be avoided. Choose a station with no obstructions above an 
inclination of 15° to 20°. Draw a station obstruction diagram to assist in the 
planning of GPS sessions. Verify the station's accessibility and then draw 
maps with directions to the stations and mark each station clearly. The field 
crew will be in a hurry to set up when they arrive, and unmarked stations can 
waste valuable time. 



TRIANGULATION 



3-3. During special surveys when the need to locate the position of a point 
that cannot be occupied arises, triangulation is necessary. This technique 
places special demands on the recon party. The mathematical computations 
place stringent requirements on the size and shape of the geometric figures 
that are used to determine coordinates. For this reason, the location of the 



Survey Recon 3-1 



FM 3-34.331 



TRAVERSE 



EDME 



stations will normally be dictated to the field-recon party, based on the results 
of the office recon. The recon party must ensure that the observation stations 
which form the baseline are intervisible. A thorough knowledge of 
triangulation criteria is absolutely necessary. 



3-4. The demands for a traverse recon are less stringent than for 
triangulation. Ensure that both the rear and the forward stations are visible 
from each proposed station. Wherever possible, distances between stations 
should be uniform. I n control surveys that may become part of the US 
National Control Network, theSSGCN must be satisfied. Spacing between 
stations will be dependent on the EDME available. 



3-5. An EDME traverse recon requires intervisibility between stations. The 
minimum and maximum allowable distances are based on the EDME 
characteristics and the clearance above possible obstructions. Use of infrared 
EDME will be dependent on the weather. 



DIFFERENTIAL LEVELING 



3-6. Differential leveling should follow routes containing the least amount of 
change in elevation between BMs and individual setups. The routes will 
frequently follow roads with moderate traffic, so care must betaken to ensure 
the safety of the leveling party. 



TRIGONOMETRIC LEVELING 



3-7. A trigonometric-leveling recon is accomplished when a traverse recon is 
performed. When given a choice between a relatively level, a greatly elevated, 
or a depressed observation, select the relatively level observation. Failure to 
accurately level the instrument will cause a greater error in an elevated or 
depressed observation. 



OTHER CONTROL METHODS 



3-8. Recon for other control methods will vary according to the physical 
characteristics and limitations of the equipment or system used. No matter 
what system or equipment is being used, the proposed station must be 
accessible and the proposed station must be able to be included in the local 
survey-control scheme. Stations occupied by PADS must not exceed the 
maximum distance and time from the initializing station. 



RECON-PARTY COMPOSITION 



3-9. The recon party will vary in disposition and number according to the 
method of survey, the type of terrain, the available transportation, the extent 
of the survey, and the density of control required. The chief of the recon party 
is normally the section leader. The recon party usually consists of two to five 
personnel. As a minimum, it will include the survey-party chief and the 
section leader. It is also helpful to include personnel who will be instrument 



3-2 Survey Recon 



FM 3-34.331 



operators. The most qualified unit members should be assigned to the recon 
party, because a properly designed recon will result in a survey project that is 
accurate, complete, and expeditious. The recon party should be thoroughly 
briefed on the project instructions and the specifications of the survey mission. 
Recon is accomplished in three phases— office recon, field recon, and recon 
reports. 



SECTION II - RECON PHASES 



OFFICE RECON 



3-10. The office-recon phase includes the gathering of existing data and a 
study of applicable maps. This phase will be completed before the start of the 
field-recon phase. 



EXISTING DATA 



3-11. During the office-recon phase, the first step is to gather all existing data 
on the area to be surveyed. Depending on the area, there may be a number of 
sources that maintain some type of rel i able survey data. The existing data will 
usually consist of trig lists, station description cards, and aerial photographs 
or maps. Trig lists come in many forms, depending on the publishing agency. 
A trig list may be compiled on DA Form 1959, horizontal-control data booklets 
from the National Geodetic Survey (NGS), or a computer printout of 
coordinates. Sources of information include— 

• Local Army units (such as map depots, FA target-acquisition (TA) 
units, SIC, and survey units). 
The NGS and the US Geologic Survey (USGS). 
USACE district offices. 

The US Department of the Interior, Bureau of Land Management. 
State and local government civil-engineering or survey offices. 
Other nations. Existing data is sometimes received from the national 
agency charged with the mapping of that nation. Local municipalities 
and city governments also have survey information in their 
engineering or land-planning offices. 

• Continuously operating reference stations (CORSs) for CON US. 

3-12. Regardless of the information source, all trig lists (officially classified or 
not) must be safeguarded. Once secured, this information should be 
maintained as a database for that area since it may be necessary to conduct 
additional surveys in the same or an adjacent area. 



MAPS 



3-13. Do not evaluate the existing material until all material has been 
assembled and the information has been annotated on the available maps or 
aerial photographs. Plot the required SCPs from the project directive, and 
then evaluate the usability of existing controls. Compare the required control 
method with the existing control method to determine if additional, basic 
control is needed. It is possible that many required stations may be eliminated 



Survey Recon 3-3 



FM 3-34.331 



because adequate control already exists. For those required stations that must 
be established, a tentative route of survey is annotated on the maps. 



FIELD RECON 



3-14. Thefield-recon phase is different for each survey project. A party chief 
must consider and apply the lessons learned from previous projects. The 
methods and techniques can be changed to suit the conditions of the current 
project. A successful party chief will also employ the knowledge and ingenuity 
of the survey-party personnel. 



INSPECTION 



3-15. When time permits, the party chief and one other person will conduct a 
preliminary field inspection of the area. When gathering information 
concerning the area to be surveyed, include terrain types, tree heights, road 
width, road surfaces, spacing between roads, microclimate (fog, haze, and heat 
waves), and any other factors that will affect distance measuring and 
intervisibility between proposed stations. The inspection may be conducted 
using vehicles, helicopters, or airplanes. The results of the inspection will 
determine the scheme and route for the survey. 

RECOVERY AND VERIFICATION OF EXISTING CONTROL STATIONS 

3-16. I n areas where control is to be extended or established, there may be 
control stations from earlier surveys that must be recovered and verified. 
These stations should have been identified and annotated on overlays during 
the office-recon phase and will serve as starting points for proposed GPS 
networks, traverse lines, or level lines. The existing stations should be 
located, described, and verified for accuracy, before using them for extending 
control . 

Existing Control Stations 

3-17. Existing control stations (and their establishing surveys) follow similar 
patterns. Recognizing and associating the patterns with the terrain types will 
assist the surveyor in locating existing stations. 

• Triangulation stations are usually found on the highest point of a hill 
or a mountain. In areas of little relief, the stations may be located at 
prominent points or sites where a tower could have been easily 
erected. 

• BMs and traverse stations are typically located along roads, railroads, 
pipelines, or other transportation routes, which permit intervisibility 
and accessibility. BMs and traverse stations may also be found along 
waterways, rivers, canals, and coastlines. 

Available Information 

3-18. I n some areas, urbanization has changed road or drainage patterns. I n 
rural areas, land may have been cleared and cultivated or fields may have 
become overgrown or reforested. Gather and consider all available 
information when searching for a station. 



3-4 Survey Recon 



FM 3-34.331 



3-19. Trig lists, control cards, and control bulletins contain brief descriptions 
and sketches of stations. The information may be outdated or insufficient for a 
final product but will permit surveyors to locate the general vicinity of the 
station. The final steps in locating the station will involve the use of distances 
and azi muths from the reference marks (RM s) to the station. 

3-20. Previous survey data may include survey schemes, overlays, or plots 
depicting the relative position of the stations in the general area. After one or 
more stations have been recovered, the other stations may be roughly plotted 
and located using a magnetic compass and either intersection or resection 
methods. 

3-21. Aerial photographs may be used if the station to be recovered can be 
identified on the photographs. Using features that are permanent and 
prominent on both the photograph and the ground will permit surveyors to 
reach the station site. 

3-22. Maps with the plotted coordinates of the station will permit surveyors to 
identify the route of travel to the station. Maps will also assist surveyors in 
determining the station's accessibility. 

3-23. Local information sources include local surveyors, public-service 
officials, construction companies, and landowners. Local sources may be the 
only means of locating a station if the area has dramatically changed si nee the 
other sources of information were published. 



Station Verification 



3-24. Verification of a station must be performed before using the station. 
Where only one other station is intervisible, a check-distance measurement 
can be performed using the GPS or a conventional method. Where two or more 
stations are intervisible, check-angle observations or GPS measurements can 
be performed. After the measurements and observations have been performed 
and reduced, they will be compared to the published information. If the 
results agree within the overall specifications for the survey project, the 
stations may be used. 



SELECTION OF NEWSTATION SITES 



Considerations 



3-25. New station sites will be selected after all existing stations have been 
recovered, described, and verified. The new stations will be placed where 
required to complete the scheme of the survey. 



3-26. Correct selection of a new station site will save time and expense and 
will prolong the life of the new station. Consider the following paragraphs 
when selecting a new station site. 

3-27. Permanency. Monuments (also referred to as marks or markers) can 
be permanent or temporary. 

• Permanent monuments. Permanent monuments are set in a 
relatively stable material or structure for the purpose of preserving 
the location of either horizontal or vertical control. Consider another 



Survey Recon 3-5 



FM 3-34.331 



site if the proposed site may experience disturbance or land 
development. Sincetherearea wide variety of possible situations that 
may be encountered when setting a monument, it is impossible to 
address them all. The ultimate selection of the site is at the discretion 
of the monument setter. 
• Temporary markers. Temporary markers are the same as 
permanent monuments except that the preservation time required is 
less. Temporary markers shall consist of a 1- by 2-inch wooden hub (or 
larger) with adjacent guard stakes, a copper nail and washer, or a 
temporary spike that is set in relatively stable material. 

3-28. Security. Foremost on the list of considerations is a monument's 
susceptibility to damage or destruction. It is necessary to anticipate any 
construction that might occur in the area. Frequently, marks that are set in 
asphalt surfaces are paved over periodically. Marks that are set off the edge of 
the asphalt surface will stand a better chance of survival. 

3-29. Accessibility. Accessibility of the marks should be evaluated in 
selecting the site. If the mark cannot be found or conveniently occupied, its 
worth is questionable. Determine if there are nearby objects that can be used 
as references. Distances and directions from prominent reference objects are 
used to locate a mark. These distances and directions are referred to as lines 
of position (LOPs). The prominent objects are referred to as origins. At least 
two LOPs are required to describe a point. The closer to perpendicular that 
the angle at which the LOPs intersect, the more accurate a position can be 
described. 

3-30. Stability. All marks are subject to the effects of geologic and soil 
activity. Vertical -control marks or BMs are particularly vulnerable because 
this activity results in vertical movements much morethan horizontal motion. 
Selecting advantageous topographic features (such as the crests of hills) will 
increase soil stability and decrease frost heave and the consistency of the soil 
will tend to be more firm. Also consider the soil-grain size, and when possible, 
choose a site with coarse-grained soils. Fined-grained soils (such as clays) are 
susceptible to high moisture content, which can be affected by frost and 
erosion. 

3-31. Safety. If a mark extends below the ground, there is a chance of 
encountering underground cables or pipes during installation. Evidence of 
underground utility lines can often be observed at the surface. Waterlines are 
marked by valve boxes, and in structures newer than 1960, the utilities are 
likely to be buried. Avoid digging near light poles, phone lines, or electric and 
gas junction boxes. 

3-32. Visibility. Select sites that provide maximum visibility above the 
horizon, plus 15°. Any obstruction above 15° will potentially block satellite 
signals. The ideal site should have visibility in all directions above 15°; 
however, in some locations at specific times, an obstruction in one or two 
directions may not affect the ability to use the site for GPS surveying. 
Existing BMs should be used as GPS monuments as often as possible. New 
marks should be located as close as possible to a known vertical control. 
Maximum effort should be made to locate all GPS-type monuments within 
100 feet of easy access to ground transportation. 



3-6 Survey Recon 



FM 3-34.331 



Station Names 



3-33. Names will normally be assigned by the customer (for example, the 
project name or number followed by the sequence number of that station in 
the scheme-of-control extension). Names should bean alphanumeric symbol 
that is stamped on the respective disk marker. The name that appears on the 
control point for publication purposes should be the same as the name that 
actually appears on the mark. Old stations that are reestablished will be 
given the previous name with a numerical suffix added (such as Boulder 
number 2). In the absence of guidance from the customer— 

• Use the name of a nearby geographical feature. 

• Use short names (maximum of 25 characters, including spaces). 

• I nclude the name of the agency or unit that set the mark if it is not 
precast. 

• Make sure the station name is spelled correctly on all documents. 

• Do not use special characters such as periods, commas, slashes, or 
equal signs. 

• Do not include nondescriptive terms such as spike or nail or personal 
names. 



Landowner Permission 



3-34. Permission must be obtained before conducting a survey on any private 
land. The survey-section sergeant or the party chief, working through the 
local J udge Advocate General (J AG), will contact and negotiate with 
landowners for access to prospective station sites. Written permission to enter 
the land is preferred because it is documented. The local J AG will assist in 
this matter and will help keep the military out of potential trouble. 

3-35. US. The recon and survey parties should have a right-of-entry letter to 
the overall area from their HQ. This letter does not entitle the survey team to 
access private property or restricted areas without further permission. When 
the landowner is contacted, a full explanation of the work to be done is given 
without any attempt to conceal any inconveniences or damage that may arise. 
Government regulations concerning damage claims should be explained when 
necessary. I n the case of an absentee owner, who cannot be reached in person, 
a letter explaining the work and asking consent to access the property should 
be mailed. 

3-36. Other Nations. When working in other nations, the appropriate officer 
of the US embassy within that country will generally negotiate the right-of- 
entry letters for overall areas within that country. However, a right-of-entry 
letter or approval from the host nation is not always sufficient for access to all 
public lands within the national boundaries. It is sometimes necessary to 
contact the local officials where the work is to be performed. Agreements will 
be conducted according to local customs. Some countries consider an oral 
agreement, or any statement that could be construed to be an oral agreement, 
to be contractual and binding. Any transfer of assets (material or otherwise) 
require close coordination with thej AG. 



Survey Recon 3-7 



FM 3-34.331 



MONUMENTATION 



3-37. The setting of stations should be accomplished during the recon phase. 
The selection of the monument type is based on local site conditions. The types 
of marks to be used for vertical and horizontal control are a function of the 
order and accuracy of the survey, the intended use of the data collected, and 
the site conditions. 



Surface Station Marks 



3-38. A variety of standard monuments (described below) are currently 
available for use as surface station marks. On projects conducted for Nl MA or 
theUSACE, standard NIMA or USACE disks should be used. The disks are 
set in the top of a concrete post or another appropriate monument. Each 
survey method has individually designated disks. These station marks must 
be as permanent as possible, intelligently placed for present and future use, 
and safe from damage. I n cultivated fields or in pastures (which may later be 
cultivated), the owner's permission should be obtained to build rock cairns or 
to set guard or witness posts around monuments. 



Subsurface Station Marks 



3-39. Subsurface station marks are used for first-, second-, and third-order 
stations. Pipe, rebar, and sectional rods are considered subsurface marks and 
aid in the relocation of disturbed marks. Where bedrock is exposed and a 
TypeC monument is used, no such mark is feasible, and the drill hole itself is 
sufficient. 



Monument Types 



3-40. The type of monument used depends on theterrain, the climate, and the 
soil composition. Engineer manual (EM) 1110-1-1002 identifies specifications 
for survey markers and monuments. Monuments can be subdivided into two 
general categories— standard and nonstandard. 

3-41. Standard Monuments. Standard monuments use some form of 
standard survey disk. These disks may be brass, bronze, aluminum, or other 
alloys. Tables 3-1 and 3-2 suggest the type of monument to be used according 
to required vertical and horizontal accuracy (USACE standards). A TypeG 
monument is sufficient for all third-order surveys, both vertical and 
horizontal. 



Table 3-1. Site Conditions and Monument Types for Vertical Control 



Site Condition 


Monument Type 


Order of Accuracy 


1 


2 


3 


Rock outcrops and concrete structures 


C 


C 


C 


Sand, gravel, till, silt, and clay 


A 


A 


G 


Construction fill (disturbed earth) 


A 


A 


A 



3-8 Survey Recon 



FM 3-34.331 



Table 3-2. Site Conditions and Monument Types for Horizontal 

Control 



Site Condition 


Monument Type 


Order of Accuracy 


1 


2 


3 


Rock outcrops and concrete structures 


C 


C 


C 


Sand, gravel, till, silt, and clay 


G 


G 


G 


Construction fill (disturbed earth) 


G 


G 


G 



TypeG monument. This classic, standard monument is made 
completely of poured concrete with a disk set in thetop of theconcrete 
(Figure 3-1, page 3-10). These procedures and dimensions are for a 
second- or higher-order monument. A TypeG monument is 
constructed by excavating a hole that is 15 centimeters in diameter 
and 60 centimeters deep. In areas where the maximum frost depth is 
greater than 60 centimeters, the hole should be 30 centimeters below 
the frost depth. The disk should be driven onto a pipe, a rod, or a 
number 5 rebar that is 120 centimeters long. The pipe, rod, or rebar 
assembly is then driven into the center of the hole until the top is 
slightly above the surface. The hole is then filled with concrete, which 
must not cover the disk. The use of pipe, rod, or rebar is optional. The 
disk may be pushed directly into the fresh concrete, but a magnet 
must be placed in theconcrete if the bar is omitted. 
Type C monument. Sound bedrock is the most desirable location for 
a BM, as illustrated by Figure3-2, page3-10. It provides the most 
stable setting in terms of underground activity and potential 
disturbances. Always use bedrock when a suitable outcrop exists. Use 
a star drill to make a hole about 2.5 centimeters wide and 6 
centimeters deep to receive the shank of the marker. Fill the hole with 
epoxy resin and insert the disk, with the resin slightly built up around 
the edge. When a solid bench or ledge is covered with a few feet of top 
soil, the subsurface mark should be in the ledge and a concrete 
monument should beset above it to protrude above the surface. 
Type A monument. Use a Type A rod monument (Figure 3-3, 
page3-ll) when sound bedrock or substantially stable structures are 
not available. The monument provides the extra horizontal stability 
required for 3D surveys, which makes the monument a suitable GPS 
mark. Refer to EM 1110-1-1002 for details on installing a TypeA 
monument. 

NOTE: TypeA monuments are used in marshes. TypeG 
monuments are used in permafrost areas. 

Precast monument. To eliminate the need for mixing and pouring 
monuments at the site, precast monuments may be used if the project 
specifications permit. These precast monuments are fabricated at the 
base station or camp and are constructed with the equivalent 
dimensions listed for poured concrete. If a subsurface mark is 



Survey Recon 3-9 



FM 3-34.331 



/////////W/M\ ■ * kW^*^ 



Concrete 



Pipe, rod, or rebar 
(optional) — 




Standard USACE 
survey disk 



E 
o 
o 




In-situ soil 



Figure 3-1. Type G Monument 



Countersink disk flush 
with surface 



Rock or 
concrete 




Epoxy grout 



Drill a hole that is 
2.5 cm in diameter. 



Figure 3-2. Type C Monument 



3-10 Survey Recon 



FM 3-34.331 



Access cover 



Ground 
Survey disk . 



Finned rod section 



Concrete 



15-cm PVCpipe 



2-cm rod 



Spiral drive point 




■ Sand 



In-situ material 



•**¥ 



Aluminum rod section 
driven to refusal 



Figure 3-3. Type A Monument 

required, it is placed as identified above with a carefully plumbed 
precast monument. 

Commercial monuments. A number of commercial monuments are 
available that can be considered standard monuments. These are 
generally metal or plastic rods (with a disk affixed to the top) that are 
driven into the ground. 

RMs. RMs are usually set in the same type of monument as the main 
station, but they can be made smaller. The number of RMs used 
depends on the survey method. I n triangulation and traverse 
methods, at least two, but normally three, RMs will be set for each 
station. These marks should be located within 30 meters of the station 
and at intervals of about 120° around the station. No subsurface 
marks are used with these marks. RMs should be located where they 
are least likely to be disturbed and where direct measurements can be 
made to them from the station. It is permissible to use drill holes or 
chiseled marks in rock outcrops. 

Azimuth marks. Azimuth marks are established in connection with 
SCPs to furnish an azimuth that will be available to local surveyors 
from an ordinary ground-level instrument setup. These marks are 
used in the extension of control from the station. The readings to 
azimuth marks are observed as part of the traverse method. Azimuth 
marks are permanent monuments that are placed in a prominent and 
safe location and more than 400 meters but less than 3 kilometers 
from the triangulation station. Prominent, permanent man-made 



Survey Recon 3-11 



FM 3-34.331 



structures may also be used as azimuth marks (for example, the light 
on the top of a water or radio-station tower or the cross on a church in 
a nearby town). 

3-42. Nonstandard Monuments. These monuments can take many forms 
and, if properly installed, provide for a good, permanent control station. Some 
examples are— 

• Expended shell casings (7.62 to 105 millimeters) embedded into a 
concrete post as prepared for standard monuments. 

• Sections of rebar or pipe driven into the ground with a concrete collar 
poured around the upper 0.3 meter. 

To aid in the preservation and to serve as a means of easy recovery of 
monuments, a witness and/or guard post may be established. Witness and 
guard posts are marked to be readi ly seen and identified. 

• Witness post. A witness post is a sign or stakedriven intothe ground 
next to the station or RM . 

• Guard post. A guard post is emplaced around a station that is 
susceptible to damage from ground traffic. They are generally large 
wood stock (8 inches by 12 inches by 8 feet) or expended steel (such as 
sections of railroad rails or heavy pipe). They are usually set 1 to 
1.5 meters into the ground and secured with concrete. 



STATION DESCRIPTION AND SKETCH 



Recovery Notes 



3-43. The recon party will prepare a description and sketch of all newly 
established permanent and temporary stations and all stations recovered. 
Stations recovered, but not used, must also have a description completed. The 
description and sketch will be done on DA Form 1959 (Figure3-4) or in an 
appropriate field book. The field record is done in free hand using vertical 
gothic lettering. A final DA Form 1959 should be typed and kept with the 
official records. 

3-44. Provide a narrative report (compiled at the station site) containing all 
the information necessary to expeditiously locate the station. The description 
should enable someone totally unfamiliar with the area to go, with certainty, 
to the immediate vicinity of the station. I n conjunction with a sketch, a 
positive identification of the station and RMs should be possible. Avoid 
repetition where possible. The description should be brief (to the point), 
logical, and includethe following information. 



3-45. The authorized recovery notes are as follows: 

• New station. This is a newly established station for which no 
description exists. 

• Recovered as described. This is a station that is recovered exactly 
as described. All marks are in good condition, the distances and 
di rections are verified, and the sketch and descri ption are adequate. 
The statement alone is sufficient for the recon recovery card. 
Transcribe the old sketch and description onto the new control card. 



3-12 Survey Recon 



FM 3-34.331 



Germany 



Illesheim/L6528 



LATITUDE 

49°28' 10.47467" 



(NORTHING) (EASTING) i^^T 

5,480,852.200 (Ml 



(NORTHING) (EASTING) 



(FT) 
(Ml 



TYPE OF MARK 



170 Monument 



STAMPING ON MARK 



NA 



10°23' 10.92519" 



(EASTING) (NORTHING) 

600,444.268 



(M) 



(EASTING) (NORTHING! 



(FT) 
(Ml 



Stone Kamp 



AGENCY (CAST IN MARKS) 
NA 



WGS84 



GRID AND ZONE 



32U 



GRID AND ZONE 



331.671 



(M) 



Amsterdam 



ESTABLISHED BY (AGENCY) 

320th Engineer 



DATE 

November 96 



ORDER 

Third 



GRID AZIMUTH, ADD 



TO THE GEODETIC AZIMUTH 



GRID AZ. (ADD) (SUB.) 



TO THE GEODETIC AZIMUTH 



AZIMUTH OR DIRECTION 
(GEODETICXGRID) 

(MAGNETIC) 



BACK AZIMUTH 



GEOD. DISTANCE 
(METERS) (FEET) 



GRID. DISTANCE 
(METERS) (FEET) 



The station is located on Storch Barracks, lllesheim, Germany. 

To reach the station front gate of Storch F3arracks (Grid 0082) go straight for 
0.1 mile to four-way intersection. Turn right (west) and proceed 0.8 mile to the gate 
of the access road and a guard shack. Follow the access road around the 
perimeter of the airfield for 0.9 mile to the station site. 

The station is a Type 70 monument protruding 20 cm above the ground and is 
located atop a burm. 

The station is located 75.1 m at an azimuth of 160° from Building 6680, 82.3 m 
from the hot fuel point and 67 m from the fuel point sign. 

Horizontal position was established by third-order class I traverse. 

Elevation was established by third-order leveling procedures. 



& 



& 



&> 



Building 6680 



Fuel 
point 



[ Berms | f [_ 



Kamp 



t 



SKETCH 



DA FORM 1959, OCT 64 



REPLACES DA FORMS 1959 
AND 1960, 1 FEB 57, WHICH 
ARE OBSOLETE. 



DESCRIPTION OR RECOVERY OF HORIZONTAL CONTROL STATION 

For use of this form, see FM 3-34.331 ; the proponent usapa vi .oo 

agency is TRADOC. 



Figure 3-4. Sample of DA Form 1959 



Survey Recon 3-13 



FM 3-34.331 



Recovered. This is a recovered station with changes that make the 
old sketch and description inaccurate or inadequate. Complete a new 
card and make a new sketch and/or description of the station. Report 
any alterations to the station or RMs and describe the altered marks 
and new measurements of the referenced distances and directions. An 
effort should be made to improve all sketches and descriptions. 
Not recovered. This is a station for which no positive evidence of 
existence can be found after a diligent search has been made. 
Destroyed. This is a station at which there is positive evidence that 
the station did exist, but the station and its RMs have been so 
mutilated that it cannot be replaced within 1 centimeter of its original 
position. The individual making the recovery and writing the 
description must use judgment in determining the status of a station. 
A station may be destroyed for precise purposes but still be valuable 
for surveys requiring less accurate control (for example, gravimetric, 
magnetic, or astronomic surveys). 

Reset. This is a station at which the monument and/or station marks 
have been replaced so that the mark is within 1 centimeter of its 
original position. A station is reset only from subsurface and/or RMs 
that have not been moved from their original positions. The task of 
resetting monuments may be assigned to the recon party. 
Disturbed. This notation is generally used only with reference to 
vertical control points. It is a station at which the monument is 
physically present, but it has been so moved that it has lost its value 
as a vertical control point within the accuracy to which it was 
originally established. 



General Location 



3-46. This information follows the recovery note. It identifies the location of 
the station area on a map in relation to cities and towns, bridges, and other 
major landmarks. The political subdivision should also be stated. 



Route Description 



3-47. This describes the route to the station site. The description should start 
from an easily located point such as a public building, a park, a main-road 
intersection, or any other permanent landmark that is identifiable both on the 
map and on the ground. Distances between checkpoints on the route are given 
in miles and tenths of miles or kilometers and meters. Changes in route 
direction are given as both left or right and east (E), west (W), north (N), or 
south (S). 



Station-Site Description 



3-48. Describe the exact location of the mark in relation to readily identifiable 
RMs. List the magnetic azimuth and the distance from the reference point to 
the station mark. 



3-14 Survey Recon 



FM 3-34.331 



Station-Mark Description 

3-49. Describe the actual mark (for example, drill hole, bronze disk, or 
chiseled mark in stone) and the exact stamping on the mark (agency, year, 
and type of station). Note if the station mark is above or below the ground's 
surface. 



RMs 



Azimuth Mark 



3-50. Describe RMs in the same manner as the station mark. I nclude the 
distances and directions measured from the station mark. 



3-51. Describe the azimuth mark in the same manner as RMs. The distance is 
usually approximated rather than measured. 



View From Tripod Height 



3-52. Describe the field of view from tripod height. For example, the view is 
unobstructed in all directions except south and the trees (60 feet high, 
300 feet from the station) obstruct the view between the magnetic azimuths of 
170° and 215°. 



Miscellaneous I nformation 



Sketch 



3-53. List any important information about the station site (which is not 
covered elsewhere) in the notes at the bottom of the description. This may 
include a photo number and mission (if applicable), danger areas, or access 
concerns. 



3-54. The sketch should be clear and simple and contain only enough detail 
for positive identification of the station. In general, it should contain the— 

• Features of a permanent nature. Show the features around the 
station with enough detail so that they will not be confused with other 
similar features. For example, many road intersections and hilltops 
look alike. Extend the sketch slightly so that the characteristic 
features become evident. When there is little detail available, make a 
rough contour sketch. Use only standard topographic and military 
symbols on the sketches. 

• Scope and scale. J udgments on what features are actually required 
to identify the station and the individual's ability to draw will usually 
govern the scope of a sketch. Normally, a sketch should include the 
area within a radius of 200 feet to 1/2 mile. Avoid sketches that cover 
an area of several miles. In all cases, the termination point of theto- 
reach site must be on the sketch. The sketch does not need to be 
drawn to scale. 

• Orientation. The sketch must be oriented to the north. 
DA Form 1959 has a preprinted arrow to indicate the direction. 



Survey Recon 3-15 



FM 3-34.331 



TRANSPORTATION 



3-55. The recon party will use transportation that is organic to the unit 
according to the unit's TOE and SOPs. When available, due to project 
requirements or customer support, using aircraft will enhance the project 
recon. Helicopters can greatly assist and speed recon efforts (for example, 
checking routes of travel and lines of sight between stations, selecting and 
identifying stations, and determining the scheme for extending surveying 
control). If aircraft are used, it is mandatory that the pilots be thoroughly 
briefed on the survey project. Complete knowledge of the entire project by the 
pilots will expedite the field recon and accelerate the progress of the project. 



COMMUNICATION 



LOGISTICS 



3-56. The recon party has access to radios, according to the unit's TOE and 
SOPs. Surveyors use the radios to confirm lines of sight when stations are 
separated by great distances. Before using the radios on a survey project, the 
party chief will obtain authorized frequencies from the local (customer's) 
signal officer. Surveyors will use the radios according to local CEOI and 
communications-electronics standing instruction (CESI). Surveyors will also 
follow the unit's standing signal instructions (SSI ), signal operation 
instructions (SOI), and radio-communications procedures. In the event of a 
conflict, the procedures of the local signal office will take precedence. 



3-57. The party chief will make arrangements with the customer to ensure 
that both fuel and maintenance are available for all vehicles. He will also 
ensure that adequate space is available to secure equipment and to perform 
project administration and field-office computing. 



RECON REPORTS 



3-58. Upon completion of the field recon, the party chief will submit a recon 
report. If the area or the project is large, the project will be divided into phases 
and a report will be prepared at the completion of each phase. The recon 
report is discussed in detail in Chapter 11. 



3-16 Survey Recon 



Chapter 4 

Datums, Grids, and Coordinate References 

The discipline of surveying consists of locating points of interest on the 
surface of the earth. Points of interest are defined by spherical or planar 
coordinate values that are referenced to a defined mathematical figure. I n 
surveying, the figure may bean equipotential surface, an ellipsoid of 
revolution, or a plane. 



DATUMS 



GEOID 



4-1. The earth is an ellipsoid, not a sphere, flattened slightly at the poles and 
bulging somewhat at the equator. Datums are reference surfaces that 
consider the curvature of the earth for the mathematical reduction of geodetic 
and cartographic data. 



4-2. The geoid is the equipotential surface within or around the earth where 
the plumb line is perpendicular to each point on the surface. The geoid is 
considered a MSL surface that is extended continuously through the 
continents. The geoidal surface is irregular due to mass excesses and 
deficiencies within the earth. The figure of the earth is considered as a sea- 
level surface that extends continuously through the continents. The geoid 
(which is obtained from observed deflections of the vertical) is the reference 
surface for astronomical observations and geodetic leveling. The geoidal 
surface is the reference system for orthometric heights. 



ELLIPSOID 



4-3. The WGS is not referenced to a single datum point. It represents an 
ellipsoid whose placement, orientation, and dimensions "best fit" the earth's 
equipotential surface that coincides with the geoid. The system was developed 
from a worldwide distribution of terrestrial gravity measurements and 
geodetic satellite observations. Several different ellipsoids have been used in 
conjunction with the WGS ellipsoid. Several ellipsoids are used in US military 
mapping. The goal is to eventually refer all positions to the WGS, which has a 
specific set of defining parameters, or to a WGS-compatible ellipsoid. 
Ellipsoids may be defined by a combination of algebraically related 
dimensions such as the semi major and semi mi nor axes or the semi major axis 
and the flattening. Figure4-1, page4-2, illustrates the defining parameters of 
some ellipsoids used by NIMA. 



PROJ ECTIONS 



4-4. A map projection is the systematic drawing of lines representing the 
meridians and parallels (the graticule) on a flat surface. Different projections 



Datums, Grids, and Coordinate References 4-1 



FM 3-34.331 









b^"N 






X 




^sT^^ N 


/^ V it \ \ 










\ 








v\ \ 


/ / f 


^\^ \ 


/ yV 


\ 




r^^ / 








L — - J ^ S 






Ellipsoid 


a(m) 


b(m) 


*1/f 




Airy 


6,377,563.396 


6,356,256.910 






Australian national 


6,378,160 




298.25 






Bessel 


6,377,397.155 




299.1528128 






Clarke 1 866 


6,378,206.4 


6,356,583.8 








Clarke 1880 


6,378,249.145 




293.465 






Everest 


6,377,276.345 




300.8017 






Hough 


6,378,270 




297 






International 


6,378,388 




297 






Modified Airy 


6,377,340.189 










Modified Everest 


6,377,304.063 




300.8017 






South American 1969 


6,378,160 




298.25 






WGS72 


6,378,135 




298.26 




'Flattening is the ratio of the difference between the semimajor axis and the semiminor axis of the 




spheroid and its major axis ta ~ ' and may be stated by the numerical value of the reciprocal of the 






flattening (1/f). 











Figure 4-1. Defining Parameters of Ellipsoids 

have unique characteristics and serve differing purposes. Projecting the 
graticule of the ellipsoid onto a plane depicts the projections. The intersections 
of the graticule are computed in terms of the ellipsoid. 



4-2 Datums, Grids, and Coordinate References 



FM 3-34.331 



GRIDS 



4-5. US military maps use the sexagesimal system of angular measurement 
(the division of a full circle into 360°) for designating the values of the 
graticule. A degree is divided into 60 minutes, and each minute is divided into 
60 seconds. Parallels are numbered north and south from 0° at the equator to 
90° at the poles. Meridians are numbered east and west from 0° at the prime 
meridian to a common 180° meridian. The prime meridian used for US 
military mapping and charting coincides with the Bureau International de 
I'Heure defined as zero meridian, located near Greenwich, England. 

4-6. The projections used as the framework of all US military maps and 
charts are all conformal. Conformability indicates that small areas retain 
their true shape; angles closely approximate their true values; and, at any 
point, the scale is the same in all directions. The following projections, which 
show military grids, are prescribed for US military topographic mapping and 
charting: 

• Maps at scales larger than 1:500,000 for areas between 80° south and 
84° north are based on the Universal Transverse Mercator (UTM) 
Projection. 

• M aps of the polar regions (south of 80° and north of 84°) are based on 
the U niversal Polar Stereographic (UPS) Projection. 

These projections are being replaced by the WGS and will be phased out once 
the maps have been reprinted with the WGS. 

4-7. The Mercator projection is not normally used for military topographic 
maps; however, its description serves as a basis for understanding the 
transverse Mercator projection. The Mercator projection can be visualized as a 
spheroid projected onto a cylinder tangent to the equator and parallel to the 
polar axis (Figure4-2, page4-4). When the cylinder is opened and flattened, a 
distortion appears. The distortion becomes more pronounced as the distance 
from the equator increases. The Mercator projection istransversed by rotating 
the cylinder again until the spheroid is parallel to a second axis (the 
meridian), which is then open and flattened (Figure4-3, page 4-5). For 
military purposes and to minimize distortion, the transverse Mercator 
projection uses 60 longitudinal zones, each 6° wide. 

4-8. Most military operations assume that map and ground distances are 
equivalent. However, in certain geodetic and artillery operations, where long 
distances are involved and the accuracy of results is essential, it is necessary 
to correct for the difference between distances on the map and distances on 
the ground. This is done by using scale factors from prepared tables or 
formulas. For the transverse Mercator projection, the scale factor is 1.00000 
(unity) at the lines between each zone, decreasing inwardly to 0.9996 at the 
central meridian (CM) and increasing outwardly to about 1.0010 near the 
zone boundaries at the equator. 



4-9. Grids are applied to maps to provide a rectangular system for referencing 
and making measurements. There is a definite relationship between the grid 
and the graticule, so that a corresponding geographic position can be 
determined for each grid position. M ilitary grids consist of parallel lines 



Datums, Grids, and Coordinate References 4-3 



FM 3-34.331 



Spheroid and cylinder on 
common axis and tangent 
along the equator. 




Development 
surface (cylinder) 



Origin of projecting lines 
( 3 / 4 of the way back 
along the diameter). 



: r 




































































































t -J" 






















































































































































I'i" 




































































































;■ 


















































•j,- 




















































































































































ttf 




















































lanw'tHf i?i*ihm0f w '!■ if # w ir f ir r tf «* n* if iW «ri?s*ts^iw*isr 
Flattened cylinder with developed projection. 



Figure 4-2. Mercator Projection 



4-4 Datums, Grids, and Coordinate References 



FM 3-34.331 



Development surface 
(cylinder) 




Axis of spheroid normal to 
axis of cylinder; spheroid 
tangent to cylinder along a 
meridian. 



Origin of projecting lines 
( 3 / 4 of the way back along 
i the diameter). 



Flattened cylinder with 
developed projection. 



m 1 1^ yf is-" [■" ii J af i* 1 m 1 n" id 1 



Figure 4-3. Transverse Mercator Projection 



Datums, Grids, and Coordinate References 4-5 



FM 3-34.331 



intersecting at right angles and forming a regular series of squares. The 
north-south lines are called eastings and the east-west lines are called 
northings. Each grid line is one of an even-interval selection of measurement 
units. The interval is selected according to the map scale. The military prefer 
to use the UTM grid for areas between 80° south and 84° north. 



COORDINATE REFERENCES 



4-10. Coordinates may be transformed from one grid system to another (for 
example, between the Lambert grid and the UTM grid or between different 
grid zones). The preferred method is to transform the grid coordinates from 
the first grid system to geographic positions. Then transform the geographic 
positions to the grid coordinates of the second grid system. This method does 
not change the datum. 



THE US MILITARY GRID-REFERENCE SYSTEM 



4-11. The US Military Grid-Reference System (MGRS) is designed for use 
with UTM grids. For convenience, the earth is generally divided into 6° by 8° 
geographic areas, each of which is given a unique grid-zone designation. These 
areas are covered by a pattern of 100,000-meter squares. Two letters (called 
the 100,000-meter-square letter identification) identify each square. This 
identification is unique within the area covered by the grid-zone designation. 

4-12. The MGRS is an alphanumeric version of a numerical UTM grid 
coordinate. Thus, for that portion of the world where the UTM grid is specified 
(80° south to 84° north), the UTM grid-zone number is the first element of a 
military grid reference. This number sets the zone longitude limits. The next 
element is a letter that designates a latitude bond. Beginning at 80° south and 
proceeding northward, 20 bands are lettered C through X. In the UTM portion 
of the MGRS, the first three characters designate one of the areas within the 
zone dimensions. 

4-13. A reference that is keyed to a gridded map (of any scale) is made by 
giving the 100,000-meter-square letter identification together with the 
numerical location. Numerical references within the 100,000-meter square 
are given to the desired accuracy in terms of the easting and northing grid 
coordinates for the point. 

4-14. The final MGRS position coordinate consists of a group of letters and 
numbers that include the following elements: 

• The grid-zone designation. 

• The 100,000-meter-square letter identification. 

• The grid coordinates (also referred to as rectangular coordinates) of 
the numerical portion of the reference, expressed to a desired 
refinement. 

The reference is written as an entity without spaces, parentheses, dashes, or 
decimal points. Examples are as follows: 

• 18S (locating a point within the grid-zone designation). 

• 18SUU (locating a point within a 100,000-meter square). 

• 18SUU80 (locating a point within a 10,000-meter square). 



4-6 Datums, Grids, and Coordinate References 



FM 3-34.331 



• 18SUU8401 (locating a point within a 1,000-meter square). 

• 18SUU 836014 (locating a point within a 100-meter square). 

4-15. To satisfy special needs, a reference can be given to a 10-meter square 
and a 1-meter square. Examples are as follows: 

• 8SUU 83630143 (locating a point within a 10-meter square). 

• 18SUU 8362601432 (locating a point within a 1-meter square). 

4-16. There is no zone number in the polar regions. A single letter designates 
the semicircular area and the hemisphere. The letters A, B, Y, and Z are used 
only in the polar regions, and their presence in an MGRS (with the omission of 
a zone number) designates that the coordinates are UPS. An effort is being 
made to reduce the complexity of grid reference systems by standardizing a 
single, worldwide grid reference system (for example, WGS). 



GEOGRAPHIC COORDINATES 



4-17. The use of geographic coordinates as a system of reference is accepted 
worldwide. It is based on the expression of position by latitude (parallels) and 
longitude (meridians) in terms of arc (degrees, minutes, and seconds) referred 
to the equator (north and south) and a prime meridian (east and west). 

4-18. The degree of accuracy of a geographic reference (GEORE F ) is 
influenced by the map scale and the accuracy requirements for plotting and 
scaling. Examples of GEOREFs are as follows: 

• 40° N 132° E (referenced to degrees of latitude and longitude). 

• 40°21' N 132°14' (referenced to minutes of latitude and longitude). 

• 40°21'12" N 132°14'18" E (referenced to seconds of latitude and 
longitude). 

• 40°21'12.4" N 132°14'17.7" E (referenced to tenths of seconds of 
latitude and longitude). 

• 40°21'12.45" N 132°14'17.73" E (referenced to hundredths of seconds 
of latitude and longitude). 

4-19. US military maps and charts include a graticule (parallels and 
meridians) for plotting and scaling geographic coordinates. Graticule values 
are shown in the map margin. On maps and charts at scales of 1:250,000 and 
larger, the graticule may be indicated in the map interior by lines or ticks at 
prescribed intervals (for example, scale ticks and interval labeling at the 
corners of 1:50,000 at 1' [in degrees, minutes, and seconds] and again 
every 5'). 



THE WORLD GEORE F SYSTEM 



4-20. The World GEOREF System is used for position reporting. It is not a 
military grid and, therefore, does not replace existing military grids. It is an 
area-designation method used for interservice and interallied position 
reporting for air-defense and strategic air operations. Positions are expressed 
in a form that is suitable for reporting and plotting on any map or chart 
(graduated in latitude and longitude) regardless of the map projection. 



Datums, Grids, and Coordinate References 4-7 



FM 3-34.331 



4-21. The system divides the surface of the earth into quadrangles, the sides 
of which are specific arc lengths of longitude and latitude. Each quadrangle is 
identified by a simple systematic letter code giving positive identification with 
no risk of ambiguity. 

4-22. There are 24 longitudinal zones (each 15° wide) extending eastward 
from the 180° meridian around the globe through 360° of longitude. These 
zones are lettered from A toZ inclusive. There are 12 bands of latitude (each 
15° high) extending northward from the south pole. These bands are lettered 
from A to M inclusive, northward from the south pole. 

4-23. Each 15° quadrangle is subdivided into 15, 1° zones of longitude 
eastward from the western meridian of the quadrangle. These 1° units are 
lettered from A toQ inclusive. Each 15° quadrangle is also subdivided into 15, 
1° bands of latitude northward from the southern parallel of the quadrangle. 
These bands are lettered from A to Q inclusive. Four letters may now identify 
a 1° quadrangle anywhere on the earth's surface. 

4-24. Each 1° quadrangle is divided into 60' of longitude (numbered eastward 
from its western meridian) and 60' of latitude (numbered northward from its 
southern parallel). This direction of numbering is used wherever the 1° 
quadrangle is located. It does not vary, even though the location may be west 
of the prime meridian or south of the equator. A unique reference for defining 
the position of a point to an accuracy of 1' in latitude and longitude (for 
example, 2 kilometers or less) is given by quoting four letters and four 
numerals. The four letters identify the 1° quadrangle. The first two numerals 
are the number of minutes of longitude. The last two numerals are the 
number of minutes of latitude. If the number of minutes is less than 10, the 
first numeral will be a zero (for example, 04). 

4-25. Each of the 1° quadrangles may be further divided into decimal parts 
(tenths or hundreths) eastward and northward. Thus, four letters and six 
numerals will define a location to 0.1' and four letters and eight numerals will 
define a location to 0.01'. 



GPS REFERENCE SYSTEMS 



4-26. To fully understand GPS and the positional information, it is important 
to understand the reference system on which it is based. GPS satellites are 
referenced to the WGS-84 ellipsoid. The absolute positions that are obtained 
directly from the GPS measurements are based on the 3D, earth -centered 
WGS-84 ellipsoid. Coordinate outputs are on a Cartesian system (X, Y, and Z) 
relative to an earth-centered, earth-fixed (ECEF) rectangular coordinate 
system having the same origin as the WGS-84 ellipsoid (geocentric). WGS-84 
Cartesian coordinates are then converted into WGS-84 ellipsoid coordinates 
(latitude, longitude, and height). The GPS uses the WGS-84 ellipsoid for 
geodetic survey purposes. The GPS routinely provides differential positional 
results on the order of 1 part per million (ppm), compared to the accepted 
results of 1:300,000 for NAD 83 and approximately 1:100,000 for NAD 27. 



HORIZONTAL-POSITIONING DATUMS 



4-27. One application of DGPS surveying is densifying project control. 
Densification is usually done relative to an existing datum (NAD 27, NAD 83, 



4-8 Datums, Grids, and Coordinate References 



FM 3-34.331 



NAD 27 



or local). Even though GPS measurements are made relative to the WGS-84 
ellipsoid coordinate system, coordinate differences (such as baseline vectors) 
on this system can be used directly on any user datum. M inor variations 
between these datums will be minimal when GPS data are adjusted to fit 
between local datum stations. Such assumptions may not be valid when high- 
order National Geodetic Reference System (NGRS) network densification is 
being performed. 

NOTE: NIMA provides datum transformation parameters to many 
more datums (including local). 



4-28. NAD 27 is a horizontal datum based on a comprehensive adjustment of 
the US National Control Network of traverse and triangulation stations. 
NAD 27 is a best fit for CONUS. The relative precision between initial-point 
monuments of NAD 27 is by definition 1:100,000, but coordinates on any given 
monument in the network contain errors of varying degrees. As a result, 
relative accuracy between points on NAD 27 may be far less than 1:100,000. 



NAD 83 



4-29. NAD 83 uses many more station observations than NAD 27 to readjust 
the US National Control Network. NAD 83 has an average precision of 
1:300,000. NAD 83 is based on the Geodetic Reference System (GRS) of 1980 
(GRS-80), earth-centered reference ellipsoid and, for most practical purposes, 
is equivalent to WGS 84. 

High-Accuracy Reference Networks Survey Datum 

4-30. The nationwide horizontal reference network was redefined in 1983 and 
readjusted in 1986 by the NGS. Since that time, several states and the NGS 
have begun developing high-accuracy reference networks (HARNs) for 
surveying, mapping, and related spatial-database projects. These networks 
(developed exclusively with a GPS) are accurate to 1 part in 1,000,000. 

ORTHOMETRIC ELEVATIONS 

4-31. Orthometric elevations correspond to the earth's irregular geoidal 
surface and are based on tidal fluctuations of the MSL at a specific location. 
Measured DEs, based on spirit leveling, are generally relative to geoidal 
heights. The DEs between two points are called orthometric differences. 
Orthometric heights for CONUS are generally referenced to NGVD 29 or 
NAVD 88. 

WGS-84 ELLIPSOID HEIGHTS 

4-32. G PS-determined heights are referenced to an idealized mathematical 
ellipsoid. This WGS-84 ellipsoid differs significantly from the geoid; thus, GPS 
heights are not the same as orthometric heights. Due to significant variations 
in the geoid (even over small distances), elevations cannot be directly equated 
to orthometric differences. For small project areas where the geoid remains 
fairly constant, the relationship between orthometric and ellipsoid heights can 
be obtained from computer modeling or local geoid modeling. Local geoid 



Datums, Grids, and Coordinate References 4-9 



FM 3-34.331 



modeling requires connecting to a sufficient number of existing orthometric 
BMs from which the elevations of known points can be best fit by adjustment. 



COORDINATE CONVERSION 



4-33. Numerous mathematical techniques have been developed to convert 
coordinates between NAD 83 and NAD 27. These techniques include a variety 
of multiple-parameter and multiple-regression transformation equations. 
Each technique has advantages and disadvantages in terms of accuracy, 
consistency, and complexity. To eliminate these inconsistencies, the USACE 
Topographic Engineering Center (TEC) configured a comprehensive 
coordinate-conversion software program called Corps Conversion (Corpscon). 
Corpscon is the standard for topographic survey conversions, but newer 
programs are available. Additional technical information and authorized 
software programs can be obtai ned from TE C or N I M A web sites. 



4-10 Datums, Grids, and Coordinate References 



Chapter 5 

Conventional Survey-Data Collection 

Theodolites and transits are instruments designed to measure horizontal 
and vertical angles. As optical instruments progressed, the development of 
optics allowed the telescope to become shortened to the point that the 
optics could be rotated 360° horizontally. This act of turning the telescope 
has sped up work and permitted the qualitative review of sighting and 
instrument errors. 



SECTION I - FUNDAMENTALS 



5-1. Surveys are usually performed to collect data that can be drawn to scale 
and plotted on a plan or map or to lay out dimensions shown on a design. 
Measurements for both types of surveys must be referenced to a common base 
for X, Y, and Z dimensions. The establishment of a base for horizontal and 
vertical measurements is known as a control survey. Conventional control 
surveys use two fundamental measurements— angle determination and 
distance measurement. 

ANGLE DETERMINATION 

5-2. Horizontal angles are usually turned (or deflected) to the right or left. 
The three types of angle measurements are as follows: 

• Interior angles. If angles in a closed figure are to be measured, the 
interior angles are normally read. When all interior angles have been 
recorded, the accuracy of the work can be determined by comparing 
the sum of the abstracted angles with the computed value for the 
closed loop (Figure 5-1, page 5-2). 

• Deflection angles. In an open traverse (Figure5-2, page5-2), the 
deflection angles are measured from the prolongation of the backsight 
line to the foresight line. The angles are measured either tothe left or 
to the right. The direction must be shown along with the numerical 
value. 

• Vertical angles. Vertical angles can be referenced to a horizontal or 
vertical line (Figure5-3, page5-3). Optical-micrometer theodolites 
measure vertical angles from the zenith (90° or 270° indicate a 
horizontal line). Zenith and nadir are terms describing points on a 
sphere. The zenith point is directly above the observer, and the nadir 
point is directly below the observer. The observer, the zenith, and the 
nadir are on the same vertical line. 



Conventional Survey-Data Collection 5-1 



FM 3-34.331 





Station C 




" — —-^Station B 




/* 118° 




\\ 


Station D / 


Jl05° 




120°^^!, 

87°05'/ \ s 






108° 


I \ i 

^ z Station A 

Exterior angle = 




Station E 


272 °55' 



Figure 5-1. Interior Angles on a Closed Traverse 



1 +43 



LEGEND: 

L = left 
R = right 




17°51'R 



6 + 33 



3 + 71 



Figure 5-2. Deflection Angles Shown on an Open Traverse 



OPTICAL THEODOLITES 



5-3. It is difficult to precisely set the angle values on the plates of an optical 
theodolite. Angles are determined by reading the initial and the final 
directions and then determining the angular difference between the two 
directions. Optical theodolites are generally very precise. The optical 
theodolite used by Army topographic surveyors (Figure5-4, page5-4) reads 
directly to 1" and by estimation to 0.1". Figure5-4 shows that the micrometer 
was turned to read an even 10". This is done by moving the grid lines into 
coincidence, and then the micrometer scale reading (02'44") is added to the 
circle reading (94°10') to give the resulting angle of 94°12'44". If several 
sightings are required for precision purposes, distribute the initial settings 
around the plate circle to minimize the effect of circle-graduation distortions. 
Table5-1, pages 5-5 and 5-6, illustrates the circle settings for 2 through 16 
positions for a 1" theodolite. 



5-2 Conventional Survey-Data Collection 



FM 3-34.331 



Horizon 
direction 



Horizon 
direction 




Nadir direction 



Figure 5-3. Reference Directions for Vertical Angles (Horizontal, Zenith, and Nadir) 

OBSERVATION PRECAUTIONS 

5-4. Because of the high-accuracy requirements for second- and third-order 
observations, constant precautions are necessary to counteract all error 
sources. The party chief should periodically inspect the performance of all 
observing parties. A good observer achieves the full potential of the 
instrument at all times. Signals and targets should be precisely bisected. Very 
little spread (three or fewer of the smallest increments marked on the 
micrometer) between the direct and reverse measurements should be 
consistently obtained. Proficiency can be attained only by a careful study of all 
factors affecting the accuracy of theodolite observations. Efforts should be 
made to eliminate all known error sources. Observation precautions are 
summarized as follows: 

• Instrument check. Check the instruments and targets for stability. 
If an instrument is not stable, all other refinements are useless. 

• Instrument adjustment. Pay careful attention to the parallax and 
the inclination of the horizontal circle plate. Errors introduced by the 
parallax and the inclination cannot be eliminated. 

• Signal and target centering. Plumb signals and targets directly 
over the SCP. Carefully aim signals and targets towards the observing 
station. 

5-5. Do not disturb the instrument while observing a position by releveling or 
striking the instrument or its support. Avoid any lateral thrust to a clamp, a 



Conventional Survey-Data Collection 5-3 



FM 3-34.331 



Microscope 
focusing knob 



Micrometer 
knob 



Horizontal clamp 



Spring housing 
assembly 



Optical plummet 
Circular level 



Telescope 




Reticle-illumination knob 



Sunshade 



Spring housing 
assembly 

Collimation slow- 
• motion screw 



Horizontal clamp knob 



Horizontal-circle 
drive cover 

Horizontal-circle 
drive knob 



Tribrach locking 
lever 



Tribrach 



^3 094 


7 V 


| 5 4 3 2 10 



2'40" 



UN 



2'50" 



I II 



Vertical angle = 94°12'44" 



Figure 5-4. Optical Theodolite 



5-4 Conventional Survey-Data Collection 



FM 3-34.331 



Table 5-1. Circle Settings for a 1" Theodolite 



Number 


5' Micrometer Drum 


10' Micrometer Drum 


Circle Wild T-3 Micrometer 


Two 








1 


NA NA NA 


0° 00' 10" 


NA NA NA 


2 


NA NA NA 


90° 05' 40" 


NA NA NA 


Four 








1 


0° 00' 40" 


0° 00' 10" 


0° 00' 15" 


2 


45° 01' 50" 


45° 02' 40" 


45° 02' 45" 


3 


90° 03' 10" 


90° 05' 10" 


90° 04' 15" 


4 


135° 04' 20" 


135° 07' 40" 


135° 20' 45" 


Six 








1 


0° 00' 10" 


0° 00' 10" 


0° 00' 15" 


2 


30° 01' 50" 


30° 01' 50" 


30° 02' 35" 


3 


60° 03' 30" 


60° 03' 30" 


60° 00' 50" 


4 


90° 00' 10" 


90° 05' 10" 


90° 04' 15" 


5 


120° 01' 50" 


120° 06' 50" 


120° 00' 35" 


6 


150° 03' 30" 


150° 08' 30" 


150° 20' 50" 


Eight 








1 


0° 00' 40" 


0° 00' 10" 


0° 00' 10" 


2 


22° 01' 50" 


22° 01' 25" 


22° 00' 25" 


3 


45° 03' 10" 


45° 02' 40" 


45° 02' 35" 


4 


67° 04' 20" 


67° 03' 55" 


67° 00' 50" 


5 


90° 00' 40" 


90° 05' 10" 


90° 04' 10" 


6 


112° 01' 50" 


112° 06' 25" 


112° 00' 25" 


7 


135° 03' 10" 


135° 07' 40" 


135° 20' 35" 


8 


157° 04' 20" 


157° 08' 55" 


157° 00' 50" 


Twelve 








1 


0° 00' 40" 


0° 00' 10" 


0° 00' 10" 


2 


15° 01' 50" 


15° 01' 50" 


15° 00' 25" 


3 


30° 03' 10" 


30° 03' 30" 


30° 02' 35" 


4 


45° 04' 20" 


45° 05' 10" 


45° 00' 50" 


5 


60° 00' 40" 


60° 06' 50" 


60° 00' 10" 


6 


75° 01' 50" 


75° 08' 30" 


75° 00' 25" 


7 


90° 03' 10" 


90° 00' 10" 


90° 04' 35" 


8 


105° 04' 20" 


105° 01' 50" 


105° 00' 50" 


9 


120° 00' 40" 


120° 03' 30" 


120° 00' 10" 


10 


135° 01' 50" 


135° 05' 10" 


135° 00' 25" 


11 


150° 03' 10" 


150° 06' 50" 


150° 20' 35" 


12 


165° 04' 20" 


165° 08' 30" 


165° 00' 50" 


Sixteen 








1 


0° 00' 40" 


0° 00' 10" 


0° 00' 10" 


2 


11° 01' 50" 


11° 01' 25" 


11° 00' 25" 


3 


22° 03' 10" 


22° 02' 40" 


22° 00' 35" 


4 


33° 04' 20" 


33° 03' 55" 


33° 00' 50" 


5 


45° 00' 40" 


45° 05' 10" 


45° 02' 10" 


6 


56° 01' 50" 


56° 06' 25" 


56° 00' 25" 


7 


67° 03' 10" 


67° 07' 40" 


67° 00' 35" 


8 


78° 04' 20" 


78° 08' 55" 


78° 00' 50" 



Conventional Survey-Data Collection 5-5 



FM 3-34.331 



Table 5-1. Circle Settings for a 1" Theodolite (continued) 



Number 


5' Micrometer Drum 


10' Micrometer Drum 


Circle Wild T-3 Micrometer 


9 


90° 00' 40" 


90° 00' 10" 


90° 04' 10" 


10 


101° 01' 50" 


101° 01' 25" 


101° 00' 25" 


11 


112° 03' 10" 


112° 02' 40" 


112° 00' 35" 


12 


123° 04' 20" 


123° 03' 55" 


123° 00' 50" 


13 


135° 00' 40" 


135° 05' 10" 


135° 02' 10" 


14 


146° 01' 50" 


146° 06' 25" 


146° 00' 25" 


15 


157° 03' 10" 


157° 07' 40" 


157° 00' 35" 


16 


168° 04' 20" 


168° 08' 55" 


168° 00' 50" 



tangent screw, or the electric switch. Other operational precautions for 
accurate observations are as follows: 

• Repoint on the initial target after each circle setting. 

• Check the plate level frequently. 

• Protect the instrument from wind, sunshine, and precipitation. 

5-6. When all other known precautions have been taken, one of the principal 
causes of error is horizontal refraction. Sometimes elevating the signal will 
reduce the effects of horizontal refraction, but often the only solution without 
altering the traverse is to reobserve the target under different atmospheric 
conditions. 



HORIZONTAL-DIRECTION RECORDINGS 



5-7. Procedures for recording horizontal directions arethe same for all orders 
of accuracy. Record horizontal directions on a DA Form 4253 (Figure5-5) or 
any authorized single-sheet recording forms. When operating the Al SI, use 
the appropriate recording media. In all cases, documentation should be 
completed in the field. Each time an SCP is occupied, the following 
information should be recorded: 

I nstrument make, model, and serial number. 

• I nstrument operator's name. 

• Recorder's name. 

• Weather description. 

Temperature. 

General atmospheric condition. 
• Wind. 

• Designation of the occupied station. 

Full station name. 

Year established. 

Name of the agency on the disk. 

5-8. The recording form should include the above information for each station 
observed. If an instrument, signal, or target is set eccentric to a station (not 
plumbed directly over the station mark), that item will be sketched on the 
recording form. The sketch should include thedistance and the directions that 
the eccentric item is from the station. When intersection stations are 
observed, the exact part of the point observed must be recorded and shown on 
the sketch. 



5-6 Conventional Survey-Data Collection 



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— 












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Conventional Survey-Data Collection 5-7 



FM 3-34.331 



5-9. Numbers and letters should be approximately half the height between 
lines. The recording should be centered in the block and on the bottom line of 
the block. All figures must be neat and legible. There should be no erasures or 
obscuring of the original figures. Original numbers may be crossed out by 
using a single diagonal line through the numbers. The corrected numbers 
should be written above the original entry. The person making the correction 
will initial above and to the right of the original entry and within the block 
and will explain the reason for the correction in the remarks column. No 
position will be voided or rejected on any recording media, except in the case of 
bumping the instrument or stand, which causes the instrument to become 
unleveled. If the instrument is observed to be unleveled, make a note on the 
recording media in the remarks column stating that the instrument was not 
leveled and why. All recordings will be done with black ink. Directions will be 
entered in the remarks column (in degrees, minutes, and seconds). 

5-10. The observer will check every computation on each page or sheet. The 
observer will verify the computation with a light, visible tick mark to the 
upper right of the computed numbers or will correct the numbers as described 
above. The observer will confirm that all computed numbers on the page have 
been checked by initialing at the bottom right corner of the page. 

5-11. If a recording book is used, make an index (on the appropriate page) of 
the stations from which observations were made and recorded. An index is 
also required for all other recording media, indicating where to locate 
observations from any occupied SCP. 



HORIZONTAL-DIRECTION ABSTRACTS 



5-12. Second-order horizontal-observation specifications require that an 
abstract of horizontal directions be compiled for every station at which 
horizontal directions have been observed. DA Form 1916 (Figure5-6) will be 
completed before leaving the SCP. Third-order horizontal observations require 
that the horizon closure, the corrected station angle, and the corrected 
explement angle be recorded before leaving the SCP. Readings will be entered 
opposite the proper circle position, as indicated in the field notes. The degrees 
and minutes for each direction are entered one time at the top of each column, 
and the seconds are entered for each circle position. 

5-13. Record all observed positions on the DA Form 1916. If two or more 
observations have been made for the same target, list all the observations in 
the same box and determine the mean for that position. 

5-14. Examine the listed positions. For any position that appears to vary 
greatly from the apparent mean of all the positions, check the computations in 
the field-recording book or other recording media. Be alert for a change in the 
minutes of the computed directions (angles) in the field data. Reject any 
positions that vary widely from the mean and then reobserve the positions. 
Enclose any values that are rejected by observation in parentheses and follow 
with "Ro." 

5-15. Compute the mean of the observed positions. Round the mean value of a 
direction to the nearest 0.1" if a 1" instrument was used for observation. 
Reject all observations that differ from the mean by more than the rejection 
limit. Enclose any rejected observations in parentheses and follow with "Rl." 



5-8 Conventional Survey-Data Collection 



FM 3-34.331 













ABSTRACT OF HORIZONTAL DIRECTIONS 

For use of this form, see TM 5-237; The proponent agency is TRAD0C. 




LOCATION 

Missouri 


ORGANIZATION 

99th Eng Det (Survey) 


STATION 

LAKE (USC&GS) 1932 


OBSERVER 

SGT Smith 


DATE 

2 April 1989 


INST. (TYPE] (NO.) 

Wild T-2 # 28234 


POSITION 
NO. 


STATIONS OBSERVED 




BROOK 

(USACE) 

1956 


BASS 

(DMA) 
1972 




EXPLEMEN- 
TARY 
ANGLE 












(Initial) 

0»00' 


047 46 


° 


312 13 


. 


° 


. 




1 


0.00 


21.5 




38.3 










2 


0.00 


22.0 




38.1 










3 


0.00 


22.0 




37.8 










4 


0.00 


21.0 




38.3 










5 


0.00 


21.5 




38.4 


- 








6 


0.00 


22 5 
(36.0)R o 




38.0 


m\\ 


t 






7 


0.00 


21.0 




' 


P V 








8 


0.00 


21.5 


~ 


i>^ 


» 








9 


0.00 


22.0 


<b 


38.1 




MnSta 


047 46 


21.7 


10 


0.00 


21.5 




38.2 




EXPLEMEN- 
TARY 


312 13 


38.1 


11 


0.00 


22.0 




37.9 










12 


0.00 


21.5 




38.2 




Closure 


359 59 


59.8 


13 


0.00 










Error 




-0.2 


14 


0.00 
















15 


0.00 












Corrected 




16 


0.00 










MnSta 


047 46 


21.8 


Sum, 




260.0 




457.6 




EXPLEMEN- 
TARY 


312 12 


38.2 


Mean, 




21.7 




38.1 










COMPUTED BY 

SPC Jones 


DATE 

2 April 1989 


CHECKED BY 

SSG J. Zambrano 


DATE 

2 April 1989 




DA FORM 1916, FEE 


1 57 USAPPC vt.oo 





Figure 5-6. Abstracting Horizontal Directions 

Rl indicates that the value was rejected using the first mean value. The 
rejection limit will be applied to each observation with the same amount of 
accuracy as when the mean was determined. 

5-16. Reobserveany rejected positions and determine a new mean. Reapply 
the rejection limit. Enclose any positions still exceeding the rejection limit in 
parentheses and follow with "R2." R2 indicates that the value was rejected 
using the second mean value. Ensure that sufficient acceptable positions 
remain. 



Conventional Survey-Data Collection 5-9 



FM 3-34.331 



5-17. Do not reject any reading if it is within the rejection limits, unless it was 
rejected at the time of observation. If a value was rejected at the time of 
observation, check the field notes for the observer's reason for rejection. Once 
a value is rejected, it cannot be used again. 

5-18. Do not use the mean of the readings if one of two or more readings on a 
position is outside the rejection limits. Use only the reading that is within the 
rejection limits. If two readings are outside the rejection limits (one is high, 
the other is low, and the mean is within the limits), the readings must be 
rejected. If there is a progressive change in the values of the positions of a 
direction or if the mean of the first half of the positions differs appreciably 
from the mean of the last half of the positions, attempt to observe another 
complete set of positions before leaving the SCP. 

VERTICAL-OBSERVATION RECORDINGS 

5-19. Recording vertical observations (zenith distances [ZDs]) is the same for 
all orders of accuracy. Vertical observations are recorded on DA Form 5817-R 
(Figure5-7), an authorized single-sheet recording form, or appropriate media 
when operating the Al SI . In all cases, complete documentation will be 
performed in the field. In addition to the recording requirements, record the 
following information: 

• The H I above the station (recorded to the nearest 0.01 meter). 

• A sketch of the observed target (that shows the point observed on the 
target) at the bottom of the object-observed column. 

• The height of the observed target (HT) above the station being 
observed (recorded to the nearest 0.01 meter). 

• A sketch showing any target's adjoining stations. This sketch will be 
drawn in the bottom of the remarks column. All possible points that 
may be observed will be measured and recorded to the nearest 
0.01 meter. 

5-20. During vertical observations, the time of the first observation of the first 
position and the time of the last observation of the last position are recorded. 
The times are recorded to the nearest whole minute. 

VERTICAL-OBSERVATION ABSTRACTS 

5-21. Vertical observations are abstracted onto DA Form 1943 (Figure5-8, 
page5-12) at the station site by the observing party. Targets or signals shown 
toother stations are sketched and dimensioned at the bottom of the form. If a 
target or signal is changed during the day, the time of the change and the new 
dimensions are also entered. 

5-22. Vertical observations recorded as vertical angles are converted to ZDs 
before abstracting. The ZDs are abstracted, including the times of the 
observations. The abstracted ZDs are meaned and reduced to corrected ZDs by 
applying the reduction to line-joining stations. The following formula is used 
to determine the reduction in seconds: 

_ , , (HI - HT)sin mean ZD 

Reduction in seconds = -y, 

,v sin 1 

where— 

s = si ope distance between stations (in kilometers) 



5-10 Conventional Survey-Data Collection 



FM 3-34.331 



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Conventional Survey-Data Collection 5-11 



FM 3-34.331 



fliCT 



Villi Ki-j I'.- ■;■ n-y 



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S Hoped 



:r.JIK<- 



! April 



-■■ ' 



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= SGBa.42] m 



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Wild ¥-3 HAULS' 



AKTHACr Of ZENITH DISTANCES 



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Figure 5-8. Abstracting Zenith Distances 



5-12 Conventional Survey-Data Collection 



FM 3-34.331 



5-23. This formula will also be applied to the vertical observations performed 
at the station at the other end of the observed line (reciprocal observations). 
The total length of the lines is multiplied by 0.46 (a constant based on the 
earth's curvature). Subtract 180° from the sum of the two corrected ZDs to 
determine the observed difference expressed as minutes of arc. If the two 
values differ by more than 1' of arc, perform a second set of reciprocal ZD 
observations. Differences exceeding V of arc are normally due to errors in 
observations or unusual refraction in the atmosphere (poor observing 
conditions). 



DISTANCE MEASUREMENT 



5-24. The distance between two points can be horizontal, slope, or vertical. A 
tape measure or an EDM device can measure horizontal and slope distances. 
In surveying, horizontal-distance measurements are always required. A 
distance measured on a slope can be trigonometrically converted to its 
horizontal equivalent by using the slope angle or vertical DE. Figure5-9 
illustrates a basic example of the geometry used to determine the horizontal 
distance of a measurement over uneven ground. 



Elevation at Station B = elevation at Station A + HI ± V - HT 
- EDM \ H(Scosa) 




nsm 



V(S sin a) 

1 



Station A 



LEGEND: 

V = vertical distance 
H = horizontal distance 
S = slope distance 



HT (measured) 
t 



Station B 



Figure 5-9. Geometry of an EDM (Basic Example) 



OBSERVATION PRECAUTIONS 



5-25. Distances measured using an EDME are subject to the same errors as 
direction measuring equipment. The errors also include instrumental 
component errors. Instrumental errors are usually described as a number of 
millimeters plus a number of ppm. The accuracy of the infrared EDME AISI is 
+(5 millimeters +5 ppm). The ppm accuracy factor can bethought of in terms 
of millimeters per kilometer, as there are 1 million millimeters in 1 kilometer. 
This means that 5 ppm equal 5 millimeters per kilometer. If the AISI is in the 
D-bar mode, the accuracy is +(2 millimeters +3 ppm). Errors introduced by 
meteorological factors must be accounted for when measuring distances of 
500 meters or more. Accurate ambient temperature and barometric pressure 



Conventional Survey-Data Collection 5-13 



FM 3-34.331 



must be measured. An error of 1 degree Celsius (C) causes an error of 0.8 ppm 
for infrared distances. An error of 3 millimeters of mercury causes an error of 
0.9 ppm in distance. 



INSTRUMENT CONSTANTS 



5-26. Although manufacturers provide instrument and prism constants, it is 
essential that instrument constants be verified under actual operating 
conditions, especially for precise surveys. The following factors must be 
considered: 

• The use of a prism typically provides an indicated distance longer 
than the true value. Applying a negative correction will compensate 
for this effect. Each prism should have its own constant or correction 
determined individually, and a master file should be maintained. 

• An instrument constant can be either positive or negative and may 
change due to the phase shifts in the circuitry. Therefore, a positive or 
a negative correction may be required. 

• The algebraic sum of the instrument and the prism constants are 
referred to as the total constant. The correction for the total constant 
(equal in magnitude but opposite in sign) is referred to as the total- 
constants correction, from which the instrument or prism constant can 
be computed if one or the other is known. 



UTM SCALE FACTOR 



5-27. The scale factor (a computed factor) affects the measured distance. The 
scale factor for a particular UTM zone is solely dependent on the location of 
the survey in relation to its east-west distance from the UTM-zoneCM . These 
zones are 6° wide and originate at 0° Greenwich meridian. North-south 
distances within the zone have no influence on the scale factor. The scale 
factor at the CM of UTM zones is 0.9996. The UTM scale factor toward the 
east and west from the CM increases to approximately 1.0004. Data-reduction 
procedures using the scalefactor are necessary for precise surveys. 



CURVATURE OF REFRACTION CORRECTION 



5-28. Distance measurements are not on a straight line. The earth's 
curvature and gravity affect the path traveled by the light beam. For a 
measured distance of 1 kilometer, the beam changes its path by nearly 
7 centimeters. An approximate estimate of this effect is expressed by the 
following formula: 

VD = 0.0675 V km 2 

where— 

VD =the verti cal di fferen ce 

0.0675 =the estimated effect on the path traveled by light 

km = the distance in kilometers (for example, 0.9 or 1.2) 



5-14 Conventional Survey-Data Collection 



FM 3-34.331 



EDME RECORDING 



5-29. Distances measured by EDME will be recorded on authorized single- 
sheet recording forms. Figure5-10 shows a completed DA Form 5819-R. If the 
AISI is used, the appropriate recording media is authorized. 











Field Sheet, Infrared 

For use of this form, see FM 3-34.331 ; the proponent agency is TRADOC. 




We.itKanfy&Ai-£iUe,ry 3.79 


UWNKKWN g9th £n#r company 


UA,fc 16 Mar 89 


APPROX DISTANCE „,.,,„ 

2,500 mi 


ZERO CORRECTION • 

■0.004 


CALIBRATION DATE 

7 Mar 89 


OBSERVER 

SPC Wihom 


reCoHdEr 

PfC White- 


INSTRUMENT STATION 

EUchom (99th £n#r)89 


H.I. 

2.54 mi 


ELEVATION 


ELEVATION 
INSTRUMENT 


ECCENTRICITY* 
TOWARD 

AWAY 0.000 mi 


iNsY NO 
2268 


REFLECTOR STaTIon 

BaUrath (99th En$r)89 


H.I. 
1.60 mi 


ELEVATION 


ELEVATION 
REFLECTOR 


ECCENTRICltY ■> 

TOWARD 

AWAY 0.000 mi 


PRISM NO 

K-1268 


METEOROLOGICAL READINGS 


ZD INSTRUMENT TO REFLECTOR 




TIME 


PRESSURE 
(Hfl) 


TEMP. 
(DRY) 


DISTANCE (meters) 


"* mm- 


*" c 


1 


2,52 7 


308 


INSTRUMENT 


0819 


762 


16 


2 


1,52 7 


306 


REFLECTOR 


0817 


761 


10 


3 


2,527 


311 


SUM 


1523 


31 


4 


2,527 


306 


MEAN 


762 


16 


5 


2,527 


306 


CORRECTION FACTOR (PPM) 


+5 


6 


2,527 


307 


PRODUCT = UD x PPM 

RC = PRODUCT x KT 6 


7 


2,527 


304 


8 


2,527 


320 


T - UD ± Z ± RC 
H' = (T) 2 -(d> 2 
H' = SIN 2D x T 
Hft = H' x 3.280840 


_* 


2327 


320 


10 


2,527 


307 


SUM 


25,273 


075 


UD 


1527.308 


McaN UNCORRECTED 
SLOPE DISTANCE (UD) 


2,527 


308 


PPM 


+ 5 


ZERO CORRECTION" (Z) 





004 


PRODUCT 


7636.540 


REFRACTIVE INDEX 
CORRECTION (RC) 





008 


RC 


+0.008 


CORRECTED SLOPE 
DISTANCE (J) 


2,527 


312 


DIFF.OFELEV. (d) 




UNCORRECTED HORIZON. 
DISTANCE (H') 






Obtained from Instrument Calibration. 
* Toward Eccentricity must be ADDED. 
Away Eccentrlolty must be SUBTRACTED. 


ECCENTRIC 
CORRECTION • (EC) 






HORIZON DISTANCE 
(Hm) / (Hft) 






REMARKS 


COMPUTED BY 

SSQ Zcumhr<xv\jO 


DATE 

01 Oct 96 


CHECKED BY 

SfC WCL&oni 


DATE 

01 Oct 96 


PAGE OF 




DA Form 5819-R. AUG 89 





Figure 5-10. Recording Electronically Measured Distances 



ELECTRONIC TOTAL STATIONS 



5-30. Electronic theodolites operate in a manner similar to optical 
instruments. Angle readings can be to 1" with precision to 0.5". Digital 
readouts eliminate the uncertainty associated with reading and interpolating 



Conventional Survey-Data Collection 5-15 



FM 3-34.331 



scale and micrometer data. The electronic angle-measurement system 
eliminates the horizontal- and vertical-angle errors that normally occur in 
conventional theodolites. Measurements are based on reading an integrated 
signal over the surface of the electronic device that produces a mean angular 
value and completely eliminates the inaccuracies from eccentricity and circle 
graduation. These instruments also are equipped with a dual-axis 
compensator, which automatically corrects both horizontal and vertical angles 
for any deviation in the plumb line. An EDM device is added to the theodolite 
and allows for the simultaneous measurements of the angle and the distance. 
With the addition of a data collector, the total station interfaces directly with 
onboard microprocessors, external PCs, and software. The ability to perform 
all measurements and to record the data with a single device has 
revolutionized surveying. Army topographic surveyors use the Al SI, which is 
addressed in detail in Section III. 



SECTION II - TARGETS 



5-31. A target is generally considered to be a nonilluminating signal. There 
are two general types of targets— tripods and poles. Both target types may 
incorporate variations. Targets are constructed of wood or metal frameworks 
with cloth covers. For easy bisection, a target should be as narrow as possible 
without sacrificing distinctness. Triangular-shaped targets are the easiest to 
bisect. Square- and rectangular-shaped targets are the second easiest to 
bisect. Round targets are the hardest to bisect due to problems in pointing 
during repeated observations. Round targets should be avoided whenever 
possible. A target that subtends an angle of 4" to 6" of arc is easy to bisect. 
Since 1" of arc equals 0.5 centimeter at a 1-kilometer distance, 6" of arch 
equals 3 centimeters at a 1-kilometer distance and 30 centimeters at a 
10 kilometer distance. Under adverse lighting conditions, the target width 
will have to be increased. To make a target readily visible against both light 
and dark backgrounds, use material constructed of alternating bands of red 
and white or orange and yellow. Flags may be added or the background may 
be filled with blaze-orange cloth to contrast the target. All cloth used on the 
targets should be slashed after construction to minimize wind resistance and 
to avoid pilfering in areas where cloth may be valuable. 



OPTICAL-THEODOLITE TARGET SET 



5-32. The optical-theodolite target set is precise-survey equipment that is 
generally used for short traverse lines (about 4 kilometers or less). This target 
set (Figure5-ll) consists of a lower and an upper group. The lower group 
consists of a tribrach with a three-screw leveling head, a circular bubble, and 
an optical plumbing device. The upper group contains a plate with three 
triangles; a long, level vial; and a lighting attachment. The upper group is 
removable and is interchangeable with a theodolite. 



5-16 Conventional Survey-Data Collection 



FM 3-34.331 



Centering mark 



!(►!« 



-Target frame 



Circular level 



Optical-plummet 
eyepiece 




Tribrach assembly 



Tribrach lock lever 
-Tribrach lock screw 
■ Leveling screw (3) 



Tripod 



Figure 5-11 . Optical-Theodolite Target Set 



AISI TARGET SET 



5-33. The AISI target set is a combination precise-survey target and infrared 
signal reflector. It is used for angle and distance measurements. The target 
assembly (Figure5-12, page5-18) consists of a lower and an upper group. The 
lower group consists of a tribrach with a three-screw leveling head, a circular 
bubble, and an optical-plumbing device that can be illuminated. The upper 
group contains a long, level vial; a tiltable reflector/target for short-range 
measurements; and a long-range reflector/target assembly. The long-range 
assembly contains one to eight reflector prisms and three triangular-shaped 
target attachments. The reflector/targets are nonilluminating. The short- 
range tiltable reflector/target may also be attached to a range pole that has an 
attached circular bubble level. 



Conventional Survey-Data Collection 5-17 



FM 3-34.331 



Figure Description 


1 


Prism 


2 


Special prism 


3 


Tiltable setout prism 


4 


Foot 


5 


Chuck 


6 


Knob 


7 


Twin prism holder 


8 


Sight target 


9 


Tribrach with illumination 


10 


Tribrach adaptor with level vial 


11 


Sight rod 


12 


Telescopic rod 


13 


Tripod 


14 


Complete eight prism holder 





Traversing 



12 



? 



Setting out and 
tacheometry 




Long-distance traversing 



Figure 5-12. AISI Target Assembly 



5-18 Conventional Survey-Data Collection 



FM 3-34.331 



Tripod Target 



5-34. The tripod target is the most stable, simplistic in construction, durable, 
and accurate. It ranges from a simple range pole to a tripod assembly that can 
be permanently embedded in concrete. All targets are susceptible to the 
effects of wind and precipitation. The tripod must be guyed or sand bagged 
and plumbed, and its legs should be securely set-in to prevent lateral 
movement. On uneven ground, one leg may have to be shortened or dug in to 
maintain a symmetrical appearance from all directions. 



Range-Pole Targets 



5-35. A range-pole target is used when the station does not require precise 
accuracy. The range pole is used to collect site-plan data quickly and in 
volume. 



TARGET SETUP 



5-36. Observers sometimes have a difficult and tedious task locating targets. 
Depending on the type of terrain and foliage in the area and in wooded areas 
where the targets are not profiled or silhouetted, they are very difficult to 
locate without direct sunlight shining on them. To expedite the locating of 
targets, it is sometimes necessary to illuminate the target area. Generally 
accepted procedures are as follows: 

• Use of a handheld flashing mirror. 

• Use of a strobe light or a portable light. 

• Use of vehicle headlights. 

5-37. Once a target area is located, it becomes a simple task to find the exact 
location of the target. The use of iridescent cloth on the target in place of 
regular signal cloth is recommended if the cloth can be interchanged. 

5-38. I n traverse operations where continual backsights and foresights are 
needed and where distances are not excessive, target sets can be used in a 
leapfrog technique. The actual distance a target can be seen depends on the 
background, the lighting, and the weather. Care must betaken when pointing 
a target at the observer so that the view is not distorted through the telescope. 
A disadvantage of a target set is that only one at a time may be set at a 
station. When setting a target, it must be plumbed exactly over a station. A 
target is said to be plumb when it is centered to within 2 millimeters of the 
point. 



LIGHTED TARGET SETS 



5-39. A target set is a precise-survey lighting device used for short traverse 
lines (about 4 kilometers or less). When a target set is used for night 
observations, it requires the attachment of an accessory lighting unit to the 
back of the target. The lighting unit consists of a metal hood with a light bulb 
mounted in the center. On the older target sets, the hood hangs on two small 
metal studs mounted at the top rear of the target. On the newer target sets, 
the hood slides down over the sides of the target from the rear. 



Conventional Survey-Data Collection 5-19 



FM 3-34.331 



TARGET AND TRIBRACH ADJ USTMENT 

PLATE BUBBLE 

5-40. After the plate bubble has been centered, its position is checked by 
rotating the target (or instrument) through 180°. If the bubble does not 
remain centered, bring it halfway back using the foot screws to properly set it. 
For example, if the bubble position is off the center by four division marks, 
turn the foot screws to center the bubble until it is only off by two division 
marks. The bubble should remain in this position while the target is rotated. 
The target is now level and can be used, but the error should be removed by 
adjusting the bubble tube. 

5-41. The bubble can now be adjusted by turning the capstan screws at the 
end of the bubble tube until the bubble is centered. Repeat the leveling 
procedure until the bubble remains in the center of the tube. Adjustments 
should be done in small increments, no more than half the error should be 
adjusted out at onetime. At the end of the procedure, make sure the capstan 
screws are tightly secured. 

CIRCULAR BUBBLE 

5-42. Tribrachs use a circular level for rough and plate-fine leveling. After the 
plate bubble has been adjusted, the circular bubble can be adjusted (centered) 
by turning one or more of the adjustment screws located around the circular- 
bubble assembly. 

OPTICAL PLUMMET 

5-43. The optical axis of the plummet is aligned with the vertical axis of the 
target (or instrument) if the crosshairs of the optical plummet stay 
superimposed on the center of the mark when thetribrach is revolved through 
180°. If the crosshairs do not stay superimposed, the plummet can be adjusted 
using the foil owing steps: 

Step 1. Level the tribrach and put the crosshair over the mark and mark a 

point. 

Step 2. Rotate the tribrach 120° and mark a second point. 

Step 3. Rotate the tribrach a second 120° and mark a third point. 

Step 4. J oin the three points into a triangle. 

Step 5. Draw a bisecting line from the center of the sides of the triangle to 

form the center of the triangle (Figure5-13[A]). 

Step 6. Adjust the optical plummet to the center of the triangle by loosening 

one side of the capstan screws and tightening the opposite screw 

(Figure5-13[BJ). 

Step 7. Repeat the process to verify the adjustment. 

Step 8. Ensure that all screws are snug after the adjustment is completed 

and that as little stress as possible is exerted on the capstan screws during the 

process. 



5-20 Conventional Survey-Data Collection 



FM 3-34.331 




Bisect each side of 
the triangle. 




B 



Adjust optical plummet to 
the center of the triangle. 



SIGNALS 



POINTING 



Figure 5-13. Optical-Plummet Adjustment 



5-44. Signals are survey targets that are either illuminated by natural sunlight 
or are electrically lighted by using batteries. The observations for all second- 
order, Class I triangulation and traverse are usually done at night by using signal 
lights because of more stable atmospheric conditions, which allow for better 
pointings. Observations may be made during daylight hours if the work situation 
prevents nighttime observations. The most commonly used signal light has a 5- 
inch reflector. This signal light is used for lines of sight in excess of 8 kilometers. 
Do not use the 5-inch light on lines of sight shorter than 8 kilometers. A rule of 
thumb to follow for other light sizes is to add no more than 1-inch to the 
diameter of the light size for each mile observed. 



5-45. The exact horizontal and vertical pointing of the light is very important. 
If the light is not pointed exactly toward the instrument, only a portion of the 
reflector will be observed. I n some cases, this portion will not be plumbed over 
the station mark. The instrument operator must check the pointing before 
starting the observations by viewing the light through the telescope. During 
hazy weather and especially on long lines of sight, the view through the 
telescope may appear as a bright spot surrounded by a flare. The instrument 
operator should request that the light keeper adjust the light slightly in a 
horizontal and vertical arc while it is being viewed through the telescope until 
the best pointing can be determined. The best pointing is when the light is the 
brightest. The light is then stopped and locked into position. If the lights are 



Conventional Survey-Data Collection 5-21 



FM 3-34.331 



MASKING 



FOCUSING 



stacked, the bottom light must be pointed first. It can be adjusted for 
brightness by adding or removing batteries. The light should never be 
improperly pointed to reduce its brilliance (this will create an eccentric light). 
The lighting attachment must be pointed directly at the observer to eliminate 
the appearance of uneven lighting of the target's triangles. 



5-46. A light can be masked to reduce the size and brilliance of the beam by 
covering equal portions of the lens (both above and below and to the right and 
left of the center of the glass face). Opposite sides of the glass must be masked 
equally to eliminate eccentricity. This type of masking is very good for 
distances between 6 and 10 kilometers on normal nights. A sheet of orange 
scribe paper is required, but any other color will work almost as well. When 
using the orange paper as a masking material, the light will present an 
orange glow with a brilliant white cross for the observer to pointing on. At 
maximum ranges, the orange glow is practically invisible through the 
telescope, and at minimum ranges, the glow will help in identification of the 
light. 



5-47. The light is focused by turning a screw at the rear of the bulb socket. By 
turning this screw, the position of the bulb is changed in relationship to the 
reflector. If the light is not properly focused, it will appear as a fuzzy ball in 
the telescope. The light may be focused by shining it on a flat surface about 
50 meters away and adjusting the size of the beam until it is slightly larger 
than the light reflector. When no distant object is available, a field-expedient 
procedure is to hold one's hand about 6 inches in front of the light and adjust 
the light until a dark spot the size of a quarter appears in the center of the 
beam. 



BRILLIANCE 



STACKING 



5-48. The type of light bulb and the amount of voltage being used will 
determine the brilliance of the light. The light is issued with two different 
bulbs: a standard 3.7- and a 6-volt bulb. The amount of voltage needed will 
vary depending on the lighting requirements. Various battery arrangements 
are shown in Figu re 5-14. If dry-cell batteries are not available or are too 
weak, a field-expedient procedure is to connect two lights (with 6-volt bulbs) in 
a series and then connect them to a 12-volt wet-cell battery. Never apply more 
voltage to a bulb than its rated value. 



5-49. When lights are needed from the same station to several observers, the 
signal lights are stacked, generally on a range-pole tripod (Figure5-15). If 
lights are stacked over a station, they must be leveled and plumbed over that 
station mark. The lowest light must be leveled and plumbed first, then the 
other lights should be attached and individually leveled. Care must betaken 
not to knock the other lights out of plumb when attaching additional lights to 
the pole. 



5-22 Conventional Survey-Data Collection 



FM 3-34.331 



T o lamps 



-o 




1 . Cells connected in series. Output 9 volts, 24 amperes. 



<? 



To lamps ( X 




o= 




-o 



<> 




o 



^ 




-o 



<? 




-o 



o 



s 




-o 



2. Cells connected in parallel. Output 1 1 /2 volts, 144 amperes. 



To lamps 




To lamps 





oo) (OO 





00 00 




Outputs are based on the 
assumption of dry cells with 
an average of 1 Vi volts and 
24 amperes each. 






OCR 

oo) (oo) (06 





3. Cells connected in series/parallel. 
Output 3 volts, 72 amperes. 



4. Cells connected in series/parallel. 
Output 4 1 /2 volts, 72 amperes. 



Figure 5-14. Battery Wiring Diagram 




Figure 5-15. Stacking of 5-Inch Signal Lights 



Conventional Survey-Data Collection 5-23 



FM 3-34.331 



RANGING 



5-50. When observations are made from a small (low) instrument stand, it is 
sometimes impossible to plumb the lights directly over the station mark. If 
this occurs, it is acceptable to use the lights on a range. The lights must be 
aligned on a range to all stations with a theodolite. The standard theodolite 
tripod or range-pole tripod is used as a stand and should be from 4 to 
30 meters from the station. Care must be taken to avoid introduction of 
eccentricities. 

NOTE : A target set is used as a signal in the same way as when it is used as a target. 

EXPEDIENT LIGHTING 

5-51. In the absence of a lighted target, a reflector may be used. By pointing a 
powerful, hand-held lantern flashlight at the reflector, a precise reflection will 
be returned. There are many other types of expedient lights or signals that 
can be used when standard equipment is not available or is inoperative. These 
include such things as the headlight of a vehicle, a masked lantern, a boxed 
lightbulb, or chemical illumination lights. The survey-party chief must use 
experience gained in the field and ingenuity to determine the proper 
expedient for a particular condition or problem. 



SECTION III - AISI 



5-52. The AISI is an electronic theodolite used to measure horizontal and 
vertical angles and distances. It represents these measurements on a display 
panel and can concurrently transfer them to a portable data-recording unit 
(DRU ). The DRU can then transfer the data to an external microprocessor for 
printing, plotting, and further refinement by surveying software. 



DESCRIPTION 



5-53. The Al SI has two modes— a construction-survey mode with a range of 
2 kilometers and a topographic-survey mode with a range of 7 kilometers. The 
Al SI mounts on standard military tripods and consists of the following 
modular subassemblies: 

• An electronic theodolite (a digital, automatic angle- and distance- 
reading/recording instrument with an electronic display/control 
panel). 

• A DRU (an external memory device for storing data from the 
theodolite). 

5-54. The AISI interfaces with microprocessors, printers, and plotters. It 
transfers digital data directly from its DRU (via a cable interface) to the 
microprocessor. The data is then refined by a fully integrated, 3D, ground- 
modeling, drafting-design system. The data can also be manually input to any 
CAD software program. 

5-55. The Al SI measures distances from 2 meters to 7 kilometers with a 
digital readout of 1 millimeter and is accurateto+2 millimeters +3 ppm over 
the measured distance. The horizontal and vertical angles are measured to an 



5-24 Conventional Survey-Data Collection 



FM 3-34.331 



accuracy of 1" of arc. The AISI has an electronic leveling device called a dual- 
axis compensator and adjusts for horizontal and vertical leveling with errors 
of 6" or less. The system has built-in communications with a range of 1 mile, 
an illuminated reticle for night operations, a 60-kilobyte memory capacity, 
and an alphanumeric keyboard and is powered by two dual-voltage, 
rechargeable, 12-volt nicad battery packs. 



COMPONENTS 



LEVELING 



5-56. A detailed list of components for the AISI is described in TM 5-6675- 
332-10. The basic components for the AISI are shown in Figure 5-16, page 
5-26. They are as follows: 

• A transport case. 

• A tribrach with an optical plummet, a battery pack, and a tribrach 
battery cable. 

• A lens and an eyepiece cover. 

• A DRU and a DRU/AI SI /battery cable. 

• I nternal and external nicad batteries. 

• A battery charger and a charging converter. 



5-57. The AISI uses a leveling device called a dual-axis compensator. It is an 
electronic device that senses the pull of gravity and uses two imaginary planes 
(one parallel to the instrument's face and the other perpendicular to that 
plane) at the base of the instrument for determining the level. The display 
simulates an actual bubble level, and foot screws are used to adjust the 
display bubble. The instrument then adjusts the horizontal and vertical axis 
to compensate for the instrument not being level. The working range of the 
compensator is 6'. That means that the instrument can be up to 6' off of level 
and still adjust the horizontal and vertical axis. The sensitivity of the display- 
bubble graduations is 6" in the fine-level mode and 20" in the coarse-level 
mode. 



QUICKCHECK 



5-58. A quick check is used to see if the Al SI needs to be run through a 
collimation test. This procedure should be done at least once a day and also 
every time the instrument operator changes. Any time the quick check fails, 
the AISI should be calibrated. This check compares the sightings at a point 
target in the reverse and the direct modes. Pressing the angle-measure (A/M) 
key for each sighting will show the difference in the horizontal aim (dH) and 
the difference in the vertical aim (dV) on the screen. Failure is determined 
when the check of the dH and the dV is more than 5" for horizontal and more 
than 10" for vertical from the mean. The collimation test will produce a value 
to correct the angles (F igure5-17, page 5-27). The procedures for the 
collimation test are described in TM 5-6675-332-10. 



Conventional Survey-Data Collection 5-25 



FM 3-34.331 



Transport Case 



Lens f— 
cover 



>c* 



Eyepiece 
cover 




Latches 





Tribrach battery 
cable 



Cable Bat,er V 

plug ->— ^ ox 




.On-off 
switch 



Plug for 
battery box 

Foot screw 



Tribrach 

Foot screw 



Illumination 
intensity control 




Locking 
lever 



DRU 



Optical 
plummet 



Foot screw 




DRU/AISI/battery cable 



Internal Nicad Battery 




External Nicad Battery 

Hook for tripod 




Fuse 



Cable connection 



Charging time: 14 hours. 
Use time: 2-3 hours. 



Connections for 
internal battery 



Charging Converter 



Charging time: 14 hours. 
Use time: 3-4 hours. 



Super Charger 



Connection for . 
external battery 




Plug to wall 



Plugs to converter 



Figure 5-16. AISI System Components 



5-26 Conventional Survey-Data Collection 



FM 3-34.331 




Figure 5-17. Quick-Check Example 



DATA COLLECTION 



5-59. TheAISI has two ways of collecting data— the coordinate method and 
the traverse method. In the coordinate method, all coordinates of points are 
collected in the field and all computations are conducted internally in the 
AISI. In the traverse method, all data is stored in the AISI in the form of raw 
angles and distances. This data is then downloaded into a survey software to 
compute coordinates. Surveyors determine which method to use. Table5-2 
shows the pros and cons for each method. 

Table 5-2. Two Methods of AISI Data Collection 



Coordinate Method 


Traverse Method 


Pros 


Cons 


Pros 


Cons 


Can use without survey 
software. 


User needs to have 
starting control. 


Known coordinates do not 
have to be known in the field. 


User needs to know how 
to operate the survey 
software. 


Can label/stake points in 
the field. 


Coordinates can 
not be readjusted. 


Topographic points can be 
readjusted. 






No proof of where 
or how coordinates 
were derived. 


Raw data is stored for proof of 
how the coordinates were 
derived. 





COORDINATE METHOD 



5-60. The coordinate method is used to collect coordinates for points that 
require little or no use of a survey software. Before using this method, the 
user-defined sequence (U DS) and coordinates for the starting control must be 
entered into the AISI. The result of this method is a visual display of 



Conventional Survey-Data Collection 5-27 



FM 3-34.331 



northings, eastings, and elevations. The angles are collected in Face I only. 
These points are also stored in a job file and can be converted to a points file 
with the use of survey software. 



TRAVERSE METHOD 



5-61. The traverse method is used to collect data that will be processed and 
adjusted by survey software. This method provides a digital copy of the 
collection process. The angles are measured in Face I and Face 1 1 and errors 
can be accounted for. The results can be compared to standards and 
specifications. Before starting the UDS, the starting coordinates must be 
entered intotheAISI. 



DATASTORAGE 



J ob Files 



Area Files 



5-62. The AISI is equipped with internal memory and an external memory 
device or DRU for storage of raw data, point information, and calculated 
coordinate data. Memory units make it easier to check and identify the data 
after collection. Two types of data (survey measurements [job files] and known 
coordinates and elevations [area files]) are saved in the memory. These job 
and area files consist of separate expansive memories and can be updated 
individually at anytime. 



5-63. J ob files are given a numeric, alpha, or alphanumeric title to permit 
later identification. All survey data is stored in a job file and includes the 
calculated coordinate and elevation data. When complete, these files can be 
transferred to a PC. 



5-64. Area files can be manually input and then stored or transferred from a 
PC. Several different files can be prepared in advance of the particular survey 
job. All known data can be stored for a project before departing tothejob site. 



FILE TRANSFER 



5-65. The AISI can be connected to a PC or an external DRU. Information can 
be transferred between either peripheral via a built-in serial interface. The 
instrument is connected to the DRU by a DRU/AI Sl/battery cable. The 
connection from the instrument to the PC is made with a standard 9-pin cable. 
Data transfer through the serial port requires that the standard parameters 
or protocol beset. When job and area files are transferred, they are copied but 
not erased. The original file remains in the device and serves as a backup for 
the project. Files can be deleted manually from the instrument or from the PC. 
Deleting files should only be done after the project is completed and properly 
archived. 



FILE EDITING 



5-66. The edit module allows viewing and editing of data within the recording 
device and the external DRU or directly from the keyboard of the instrument. 



5-28 Conventional Survey-Data Collection 



FM 3-34.331 



Edit functions include search, delete, insert, and change. The editing features 
are menu driven with the command options displayed on a screen. Options are 
selected using the keyboard. I n the editing module, errors such as HT and 
station number can be checked and changed by the instrument operator in the 
field to ensure correctness before leaving the site. 



COMMUNICATIONS 



5-67. TheAISI contains an internal communication system that enables 
speech communication to be carried out from the instrument to the receiver 
prism. This system is a one-way communication from the instrument to the 
reflector prism. There is a small microphone on the instrument panel that is 
activated from the control panel. When activated, the measuring beam is used 
entirely for speech transmission. This provides a communication channel 
without interference and without the need for a special radio-frequency 
permit. This type of communication relies on good planning between the 
instrument operator and the rodman to gather the appropriate data without 
errors or the need to revisit the area to fill in gaps in the collection process. 
The maximum range that this system is considered to function well is 
1,600 meters in good weather. 



INSTRUMENT MAINTENANCE 



CLEANING 



5-68. TheAISI is designed to withstand normal electromagnetic disturbance 
from the environment. However, it contains circuits that are sensitive to static 
electricity. Only the manufacturer is authorized to open the cover. To do so by 
anyone else will void the warranty. The Al SI is designed and tested to 
withstand field conditions, but like other precision instruments, it requires 
care and maintenance. Avoid rough jolts and careless treatment. 



5-69. Keep the lenses and reflectors clean. Always use lens paper or other 
material intended for cleaning optics (antistatic lens paper, a cotton wad, or a 
lens brush). Caution must be exercised when the instrument is cleaned, 
especially when removing sand and dust from the lenses and the reflectors. 
Never use a coarse or dirty cloth or hard paper. 



CONDENSATION 



5-70. After surveying in moist weather, the instrument should betaken 
indoors. The instrument should be removed from the transport case and left to 
dry naturally. Allow condensation that has formed on the lens to evaporate. 



TRANSPORTING 



5-71. Keep the Al SI protected and in an upright position when it is not being 
used or is being transported. Never carry the instrument while it is mounted 
on a tripod, because this will damage the tribrach screws. The diode used to 
send the measurement signal is sensitive to shock, especially when the 
instrument is on its side. The instrument should always be transported in its 
case with the case locked and in an upright position. For shipment, the sender 
and the receiver should be clearly marked on the transport case. 



Conventional Survey-Data Collection 5-29 



FM 3-34.331 



BATTERIES 



5-72. The AISI has two types of batteries— an internal, 1-ampere-hour (AH) 
battery and an external, 2-AH battery. Both are 12-volt, rechargeable nicad 
batteries and take 14 hours to recharge. The 1-AH battery can be fast charged 
in 2 hours and when fully charged, will supply power for 2 continuous hours. 
The 2-AH battery is attached to the tripod and connected via a special cable. It 
can supply power for an additional 4 continuous hours. The AISI can also be 
connected to a 12-volt vehicle battery. 

5-73. The batteries are charged with a 115-volt alternating current (AC) 
battery charger. Three batteries can charge simultaneously when the charger 
is connected to a charging converter. The batteries are first discharged before 
recharging begins. Once charged, the system will switch to a trickle charge to 
maintain capacity. The condition of the battery is better preserved by using 
the battery until the low-battery indicator or automatic cutoff function is 
activated. If the battery cuts off during use, the instrument will retain the 
observation or function being used for up to 2 hours whilethe battery is being 
recharged. 

NOTE: The AISI has an internal clock battery. A warning will be displayed when this 
battery is low. If this battery goes dead, the instrument will require reprogramming. 
When the warning appears, make arrangements to send the Al SI to the repair shop as 
soon as possible. The internal battery will need to be replaced about every two years. 



SECTION IV - CAD INTERFACE 



5-74. CAD software is commonly available and can produce results from basic 
survey plots to finished map sheets. Such drafting tools offer surveyors more 
accuracy, efficiency, flexibility, and quality in the production of hard-copy 
plots. CAD software, which is available through an Armywide contract, is 
used in topographic and construction survey units. 

TOTAL-STATION DATA COLLECTION AND INPUT 

5-75. Survey data can be entered into a CAD program by a variety of 
techniques. The most favorable means is through a digital data file produced 
by electronic survey equipment. Total stations, GPS-S receivers, and some 
electronic levels are commonly capable of recording survey data on electronic 
data collectors. Such logging of data greatly increases the efficiency and 
accuracy of data collection and eliminates human error associated with field- 
note recording. These digital data files also eliminate the tedious and error- 
prone manual entry of data. Automatic data logging clearly offers a superior 
method for recording and processing survey angles, distances, or coordinates, 
but it does not eliminate the requirement for field notes. To establish complete 
survey records, field personnel must always record survey conditions, the 
project description, unplanned procedures, and any other pertinent 
information. 

5-76. For total-station instruments, various software/hardware packages are 
available to collect and process survey data. The AISI and a CAD interface 
offer a full set of hardware and software for logging survey data, performing 
postprocessing and adjustments, and importing data into a PC workstation for 
further processing. CAD data-collection packages store the input of X, Y, and 



5-30 Conventional Survey-Data Collection 



FM 3-34.331 



PLOTTING 



Z coordinates in the American Standard Code for Information Interchange 
(ASCI I ) format with a descriptor or code to indicate the surveyed feature 
along with alphanumeric description data. The data can then be managed into 
more complex and sophisticated packages of information to produce map 
products of great detail. The resulting product can then be plotted in hard 
copy or transferred into a more common format. 



5-77. CAD systems offer extreme flexibility in data plotting. The sheet sizes 
are dependent on the plotter or printer. The missions commonly performed by 
topographic surveyors require a standing floor-mounted plotter that is capable 
of plotting D- and E-size sheets. I nk-jet plotters can output the most desired 
media, including paper and mylar. Plotters that use ink-jet technology are 
common, inexpensive, and easy to maintain. The quality of the plot is equal to 
or greater than that of professional, manually drafted plots. These devices 
produce objects of any shape, color, or size; eliminate the need for tedious 
manual drafting by cartographic specialists; and provide topographic 
surveyors a necessary self-sufficient capability. 



Conventional Survey-Data Collection 5-31 



Chapter 6 

Traverse 

Traversing is a form of a control survey that is used in a wide variety of 
surveys. Traverses are a series of established stations that are linked 
together by the angle and distance between adjacent points. The angles 
are measured by theodolites, and the distances are measured by an 
EDME.TheAISI total station combines both of these functions. Detailed 
information pertaining to traverse design, data collection, and limitations 
are discussed in the SSGCN. Appendix B summarizes the standards for 
control surveys. Appendix C details the recommended procedures for 
traverse computations. 

STARTING CONTROL 

6-1. The purpose of a traverse is to locate points relative to each other on a 
common grid. Surveyors need certain elements of starting data, such as the 
coordinates of a starting point and an azimuth to an azimuth mark. There are 
several ways to obtain the starting data, and surveyors should make an effort 
to use the best data available to begin a traverse. Survey-control data is 
available in the form of existing stations (with the station data published in a 
trig list) or new stations (established by local agencies who can provide the 
station data). 

OPEN TRAVERSE 

6-2. An open traverse (Figure6-1, page6-2) originates at a starting station, 
proceeds to its destination, and ends at a station with an unknown relative 
position. The open traverse is the least desirable traverse type, because it does 
not provide the opportunity for checking the accuracy of thefieldwork. All 
measurements must be carefully collected, and every procedure for checking 
position and direction must be used. Therefore, the planning of a traverse 
should always provide for closure of the traverse. 

CLOSED TRAVERSE 

6-3. A closed traverse either begins and ends on the same point or begins and 
ends at points with previously determined (and verified) coordinates. In both 
cases, the angles can be closed and closure accuracy can be mathematically 
determined. 

TRAVERSE CLOSED ON A STARTING POINT 

6-4. A traverse that starts at a given point, proceeds to its destination, and 
returns to the starting point without crossing itself in the process is referred 



Traverse 6-1 



FM 3-34.331 



JULIO 
A 



~90°10'53.6" 189°31'15.2" 

\ /-^s. 155°07'57.8" 



1 91 °32'41 .2" 



TILDON 




AIR FORCE 



MARINE 



NAVY 



ARMY 



LEGEND: 

A = control station 
O = traverse station 



Figure 6-1. Open Traverse 

to as a loop traverse (Figure6-2). Surveyors use this type of traverse to 
provide control if there is little existing control in the area and only the 
relative position of the points is required. While the loop traverse provides 
some check of thefieldwork and computations, it does not ensure the detection 
of all the systematic errors that may occur in a survey. 

TRAVERSE CLOSED ON A SECOND KNOWN POINT 

6-5. A traverse that is closed on a second known point begins at a point of 
known coordinates, moves through the required point(s), and terminates at a 
second point of known coordinates. Surveyors prefer this type of traverse 
because it provides a check on thefieldwork, computations, and starting data. 
It also provides a basis for comparing data to determine the overall accuracy 
of the work. 



FIELDWORK 



6-6. I n a traverse, three stations are considered to be of i mmediate 
significance. These stations are the rear, the occupied, and the forward. The 
rear station is the station that the surveyors who are performing the traverse 
have just moved from, or it is a point to which the azimuth is known. The 
occupied station is the station at which the party is located and over which the 
instrument is set. The forward station is the immediate destination of the 
party or the next station in succession. 



HORIZONTAL ANGLES 



6-7. Always measure horizontal angles at the occupied station by sighting the 
instrument at the rear station and measuring the clockwise angles to the 
forward station. M ake instrument observations to the clearest and most 
defined and repeatable point of the target that marks the rear and forward 
stations. Measurements are repeated according to the required specifications. 



6-2 Traverse 



FM 3-34.331 



Station B 



Station A 



Station E 




Station C 



Station D 



DISTANCE 



Figure 6-2. Closed Traverse (Loop) 



6-8. Use an EDM E to measure the distance in a straight line between the 
occupied and the forward stations. Measurements are repeated according to 
the requi red specifications. 



TRAVERSE STATIONS 



6-9. Select sites for traverse stations as the traverse progresses. Locate the 
stations in such a way that at any one station both the rear and forward 
stations are visible. The number of stations in a traverse should be kept to a 
minimum to reduce the accumulation of instrument errors and the amount of 
computing required. Short traverse legs (sections) require the establishment 
and use of a greater number of stations and may cause excessive errors in the 
azimuth. Small errors in centering the instrument, in station-marking 
equipment, and in instrument pointings are magnified and absorbed in the 
azimuth closure as errors in angle measurement. 



STATION MARKERS 



6-10. Station markers are usually 2- by 2-inch wooden stakes, 6 inches or 
more in length. These stakes (hubs) are driven flush with the ground. The 
center of the top of the hub is marked with a surveyor's tack or an X to 
designate the exact point of reference for angular and linear measurements. 



Traverse 6-3 



FM 3-34.331 



6-11. To assist in recovering a station, surveyors drive a reference (witness) 
stake into the ground so that it slopes toward the station. Surveyors must 
write the identification of the station on the reference stake or on a tag that is 
attached to the stake with a lumber crayon or a china-marking pencil. Signal 
cloth may also be tied to the reference stake to further assist in identifying or 
recovering a station. 



STATION SIGNALS 



6-12. A signal must be erected over survey stations to provide a sighting point 
for the instrument operator. The survey target set (discussed in Chapter 5) is 
the most commonly used signal. 



TRAVERSE -PARTY ORGANIZATION 



6-13. The number of personnel available to perform survey operations 
depends on the unit's TOE. The organization of these people into a traverse 
party and the duties assigned to each member will depend on the unit's SOP. 
The organization and duties of a traverse party are based on the functional 
requirements of the traverse. 

6-14. The party chief selects and marks the traverse-station locations and 
supervises the work of the other party members. The party chief also assists 
in the survey recon and planning. 

6-15. The survey team consists of the foil owing members: 

• Instrument operator. The instrument operator measures the 
horizontal angles and distances at each traverse station. 

• Recorder. The recorder keeps the field notes in a field notebook and 
records the angles and distances measured by the instrument operator 
and all other information pertaining to the survey. 

• Rodman. The rodman assists the party chief in marking the traverse 
stations, removes the target from the rear station when signaled by 
the instrument operator, and moves the target forward to the next 
traverse station. 



AZIMUTH COMPUTATIONS 



6-16. The azimuth of a line is the horizontal angle (measured clockwise) from 
a base direction to the line in question. To compute a traverse, surveyors 
determinethe azimuth for each traverse leg. The azimuth for each succeeding 
leg is determined by adding the value of the measured angle at the occupied 
station to the value of the azimuth from the occupied station to the rear 
station. On occupation of each successive station, the first step is to compute 
the back azimuth of the preceding leg (the azimuth from the occupied station 
to the rear station). 



AZIMUTH ADj USTMENT 



6-17. Determinethe need for an adjustment before beginning final -coordinate 
computations. If the angular error of closure (AEC) falls within the computed 



6-4 Traverse 



FM 3-34.331 



AE, the azimuths of the traverse may be adjusted. The allowable AEC is 
determined for third-order, Class I traverse by the following formula: 

AEC = 10" JN 

where— 

10"= AE for a singlestation 

N = the number of traverse segments 

If theazimuth error does not fall within the AEC, reobserve the station angles 
of the traverse in the field. 

AZIMUTH CORRECTION 

6-18. Before determining a correction, compute the actual azimuth error. The 
azimuth error is obtained by subtracting the known closing azimuth from the 
computed closing azimuth. This difference provides the angular error with the 
appropriate sign. By reversing this sign, the azimuth correction (with the 
appropriate sign) is obtained. 

6-19. A traverse adjustment is based on the assumption that errors have 
accumulated gradually and systematically throughout the traverse. An 
azimuth correction is applied accordingly. The correction is distributed 
systematically among the angles of the traverse. 

6-20. After the angles are adjusted, computethe adjusted azimuth of each leg 
by using the starting azimuth and the adjusted angles at each traverse 
station. Compute the adjusted azimuth throughout the entire traverse and 
check against the correct azimuth to the closing azimuth mark before 
beginning any further traverse computations. 

AZIMUTH-BEARING ANGLE RELATIONSHIP 

6-21. The trigonometric functions (such as sine [denoted by sin], cosine 
[denoted by cos], and tangent [denoted by tan]) of theazimuth and the bearing 
are numerically the same. Surveyors may use either the azimuth or the 
bearing to compute the traverse. The choice will depend on the computer and 
the equipment available. 

AZIMUTH AND BEARING 

6-22. If a calculator with angular functions is available, the use of the 
azimuth is easier since it eliminates the need to compute the bearing. If the 
functions must be determined from tables, it is necessary to first computethe 
bearing angles since the tabulation of functions is normally published for 
angles of 0° to 90°. The bearing of a line is the acute angle (an angle less than 
90°) formed by the line in question and the north-south line through the 
occupied point. The bearing illustrates the relationship between the azimuth 
of a line and its direction. 



QUADRANTS 



6-23. Bearing angles are computed from a given azimuth depending on the 
quadrant in which theazimuth lies. When theazimuth is in the first quadrant 



Traverse 6-5 



FM 3-34.331 



(0° to 90°), the bearing is equal to the azimuth. When the azimuth is in the 
second quadrant (90° to 180°), the bearing is equal to 180° minus the azimuth. 
When the azimuth is in the third quadrant (180° to 270°), the bearing is equal 
to the azimuth minus 180°. When the azimuth is in the fourth quadrant (270° 
to 360°), the bearing is equal to 360° minus the azimuth. Since the numerical 
values of the bearings repeat in each quadrant, the bearings must be labeled 
to indicate which quadrant they are in. The label must indicate whether the 
bearing angle is measured from the north or south line and whether it is east 
or west of that line. For example, a line with an azimuth of 341°12'30" falls in 
the fourth or northwest (NW) quadrant and its bearing is N 18°47'30" W. 



COORDINATE COMPUTATIONS 



6-24. If the coordinate of a point and the azimuth and distance from that 
point to a second point are known, the coordinate of the second point can be 
computed. The azimuth and distance from Station A to Station B are 
determined by measuring the horizontal angle from the azimuth mark to 
Station B and the distance from Station A to Station B. 

6-25. A grid is a rectangular system with the easting and the northing lines 
forming right angles at the point of intersection. The computation of the 
difference in northing (dN) (sideY) and the difference in easting (dE) (sideX) 
requires the computation of a right triangle. The distance from Station A to 
Station B is the hypotenuse of the triangle, and the bearing angle (azimuth) is 
the known angle. The following formulas are used to compute dN and dE: 

dN = cos azimuth x distance 

dE =sin azimuth x distance 

6-26. If the traverse leg falls in the first (northeast [NE]) quadrant, the value 
of the easting increases as the line goes east and the value of the northing 
increases as it goes north. The product of the dE and the dN are positive and 
are added to the easting and northing of Station A to obtain the coordinate of 
Station B. 

6-27. When using trigonometric calculators to compute a traverse, enter the 
azimuth angle, and the calculator will provide the correct sign of the function 
and thedN and the dE. If the functions are taken from tables, the computer 
provides the sign of the function based on the quadrant. Lines going north 
have positive dNs; lines going south have negative dNs. Lines going east have 
positive dEs; lines going west have negative dEs. 

6-28. The following are examples of how to determine thedN and the dE: 

• Given an azimuth from Station A to Station B of 70°15'15" and a 
distance of 568.78 meters (this falls in the first [NE] quadrant), 
compute thedN and the dE. 

dN =cos 70°15 15" x 568.78 =40.337848x568.78= +192.16 m 
dE =sin 70°1515"x 568.78 =+0.941200x568.78 = +535.34 m 

• Given an azimuth from Station B to Station C of 161°12'30" and a 
distance of 548.74 meters (this falls in the second [southeast] [SE] 
quadrant), compute thedN and the dE. 



6-6 Traverse 



FM 3-34.331 



dN = COS 161°12 30" x 548.74 =-0.946696x548.74 =-519.49 m 

dE =sinl 61 "12 30 "x 548. 74 = +0.322128 x 548. 74 = +1 76. 76 m 

Given an azimuth from Station C to Station A of 294°40'45" and a 

distance of 783.74 meters (this falls in the fourth [N W] quadrant), 

compute the dN and the dE. 

dN = COS 294°40'45"x 783.74 = +0.417537x783.74 = +327.24 m 

dE =sin 294°40'45"x 783.74 =-0.908660x783.74 =-712.15 m 



ACCURACY AND SPECIFICATIONS 



6-29. The overall accuracy of a traverse depends on the equipment, the 
procedures used in the measurements, the accuracy achieved, and the 
accuracy of the starting and closing data. An accuracy ratio or ratio of closure 
(RC) of 1:5,000 is the minimum accuracy sought in topographic surveying. In 
obtaining horizontal distances, an accuracy of at least 2 millimeters per 
100 meters must be obtained. When using a 1" theodolite, turn the horizontal 
angles four positions. Keep an angular closure of 10" per station. 



SEA-LEVEL COEFFICIENT 



6-30. The corrected field distances must be reduced to sea level. Along any 
traverse with variations in elevation not exceeding 300 meters, sufficient 
accuracy may be obtained by computing a sea-level coefficient (SLC) for the 
entire traverse. 



LINEAR ERROR 



AE 



RC 



6-31. To determine the acceptability of a traverse, compute the linear error of 
closure (LEC) (using the Pythagorean theorem), the AE, and the accuracy 
ratio. The first step in a closed-traverse case is to determine the linear error in 
thedN and thedE. In the case of a loop traverse, the algebraic sum of thedNs 
and the dEs should equal zero. Any discrepancy is the linear error in thedN or 
thedE. 



6-32. The AE should then be computed using the appropriate accuracy ratio 
(1:5,000 or better) and the total length of the traverse. Compare this to the 
LEC. If the AE is greater than the LEC, the traverse is good and can be 
adjusted. If the traverse is not good, it must be redone. 



6-33. TheRC determines the traverse accuracy and compares it to established 
standards. The RC is the ratio of the LEC (after it is reduced to a common 
ratio and rounded down) to the total length of the traverse. IftheRC does not 
fall within allowable limits, the traverse must be redone. It is very possible 
that the measured distances are correct and that the error can be attributed to 
large, compensating angular errors. 

6-34. The accuracy of a traverse is the ratio of error to the total length of the 
traverse. The RC must meet the specifications for the order of work being 
performed. Third-order, Class I accuracy requires an RC of 1:10,000. Accuracy 



Traverse 6-7 



FM 3-34.331 



requirements are identified in DM S ST 031. If the traverse does not meet this 
specification, no further computations are necessary. 



COORDINATE ADJ USTMENT 



6-35. Make the adjustment of the traverse using the compass rule. This rule 
states that for any leg of the traverse, the correction to be given to the dN or 
thedE is to the total correction for the dN or the dE as the length of the leg is 
to the total length of the traverse. The total correction for thedN or thedE is 
numerically equal to the error in northing (En) or the error in easting (Ee), 
but with the opposite sign. 

6-36. When adjusting a traverse that starts and ends on two different 
stations, compute the coordinates before the error is determined. The 
correction (per leg) is determined in the same manner, but it is applied 
directly to the coordinates. The correction to be applied after computing the 
first leg is equal to the correction computed for the first leg. The correction to 
be applied after computing the second leg is equal to the correction computed 
for the first leg plus the correction computed for the second leg. The correction 
for the third leg equals the correction computed for the first leg plus the 
correction computed for the second leg plus the correction computed for the 
third leg and soon throughout the traverse. The final correction must be equal 
tothetotal correction required. 



6-8 Traverse 



Chapter 7 

Differential Leveling 

Differential leveling is a technique used to determine differences in 
elevation between points that are remote from each other. Differential 
leveling requires the use of a surveyor's level together with graduated 
measuring rods. An elevation is a vertical distance above or below a 
referenced datum. In surveying, the referenced datum is typically the 
MSL. 



SECTION I - INSTRUMENTS AND EQUIPMENT 



7-1. Some of the basic components for leveling are a level, a tripod, rods, and 
accessories. A level has three major components— a telescope, a level tube, 
and a leveling head. There are three types of levels used in differential 
leveling— automatic, digital, and optical-micrometer. 

AUTOMATIC LEVELS 

7-2. An automatic level uses a gravity-referenced prism or a compensator to 
orient the line of sight automatically. The instrument can be quickly leveled 
when a circular bubble level is used. When the bubble is centered, the 
compensator takes over and maintains a horizontal line of sight. Automatic 
levels are quick to set up and easy to use and can obtain second-order, Class II 
precision. The use of an automatic level entails using a freely moving prism 
that is suspended by a fulcrum or wire as a compensator. The compensator is 
sensitive to shock and must be kept nearly upright at all times. If the fulcrum 
or wire breaks, the instrument becomes useless. Gently tapping the 
instrument, while viewing through the telescope, will cause the line of sight to 
veer slightly. This verifies that the compensator is working properly. 

DIGITAL LEVELS 

7-3. The level has been advanced, along with other survey equipment, into 
using electronic measurements. The digital level uses electronic image 
processing to determine heights and distances and to automatically record 
data for future transfer to a PC. The digital level is an automatic level that is 
capable of normal optical measurements. When used in the electronic mode, 
together with a rod face that is graduated with a bar code, the instrument 
captures and processes the image of the bar code. The processed image of the 
bar code is compared to the image of the entire rod and is programmed in the 
memory of the instrument. The difference in height and distance is then 
determined. The digital level contains predetermined programs for running 



Differential Leveling 7-1 



FM 3-34.331 



any type of line or making adjustments to a sighting. The programs store, 
compute, and transfer the data in a manner similar to that of a total station. 



OPTICAL-MICROMETER LEVELS 



7-4. Optical-micrometer levels are similar to automatic levels in design. The 
optical-micrometer level can be purchased as an individual piece of equipment 
or as an attachment for some automatic levels. Optical-micrometer 
attachments employ a plane parallel-plate lens, which when rotated will 
vertically deflect the line of sight of the incoming light ray. The optical- 
micrometer level subdivides the smallest graduation of the level rod to an 
accuracy of about +0.02 of the level-rod graduation, which means a recorded 
direct reading of 0.001 meter. FGCC standards require an optical micrometer 
be used for all first-order leveling. Some, but not all, digital levels are capable 
of meeting the required accuracy. Field operations for optical-micrometer 
leveling are nearly the same as for three-wire leveling except that optical- 
micrometer leveling uses double-scale invar rods and shorter sight distances. 



LEVELING RODS AND ACCESSORIES 

7-5. Leveling rods are manufactured of metal, wood, or fiberglass. They are 
graduated in feet or meters and can be read directly to the nearest tenth of a 
foot or centimeter (Figure7-1). To obtain a more precise reading, the reading 
is either estimated (single or three-wire method) or read with an optical 
micrometer or a digital image. Precision leveling requires one-piece rods that 
are calibrated for accuracy and thermal expansion. For less precise work, an 
extendable or folding rod may be used. The sole of the rods are made of a 
metal base, machined for accuracy. Precise rods have a built-in circular 
bubble level to maintain the plumb of the rod. Placing the rod on a stable, 
consistent surface and maintaining plumb are keys to completing accurate, 
differential-leveling measurements. 

7-6. The sole of the rod is placed on the BM or a temporary turning point. The 
turning point can beany hardened surface with a definable and reproducible 
high point. Manufactured points (for example, the marlinspike and the base 
plate or turtle) can be used. The marlinspike is a stainless-steel pin that is 
driven into soft surfaces at an angle and a depth sufficient to support the level 
rod. The portable base plate is made of cast iron with a machined-steel point 
to place the rod on. The base plate weighs 2.5 kilograms or more, can be used 
on any surface, is more stable than the marlinspike, and is a requirement for 
higher-order vertical surveys. 

7-7. There are two types of tripods available for leveling— the fixed-leg and 
the extension-leg. Either tripod is acceptable for second- and third-order 
leveling. Generally, fixed-leg tripods are preferred, but conditions and 
logistics may dictate using extension-leg tripods. 

INSTRUMENT TESTING AND ADJ USTMENT 

7-8. A collimation test for leveling (C-check) is a field determination of a 
geodetic level's collimation error (C-factor). If the instrument is placed 
precisely between two rods, the error is the same for the rear and forward 



7-2 Differential Leveling 



FM 3-34.331 



Level-rod faces 



r5 



No. 1 

Philadelphia; 

feet, 10ths, 

100ths 



:2 



1 



d 



s 



No. 2 

Philadelphia; 

meters, 
decimeters, 
centimeters 



H 

rZ 

r i 

r8 





No. 3 

Direct 

elevation; 

feet, 1 0ths, 

100ths 



No. 4 

Stadia; 

feet, 10ths, 



/ 2 1 0ths 



No. 5 

Stadia; 

meters, 

decimeters, 

centimeters 



Figure 7-1. Traditional Rectangular Cross-Section Leveling Rods Showing a Variety of 

Graduation Markings 



Differential Leveling 7-3 



FM 3-34.331 



readings and the measurement is the true DE (Figure7-2). When the sight 
distances are unequal and collimation is not true, small errors are 
accumulated. The numerical value obtained during the C-check gives the 
correction to the observed DE because of the inequality of sight distances for a 
single setup or the inequality of the accumulated sight distance for a section of 
differential leveling. Methods for observing, computing, and adjusting a level 
are discussed further in Appendix C. Surveyors should follow these 
procedures: 

• Perform a C-check at the beginning of every day that geodetic leveling 
is performed or when the level is jarred. 

• Perform a C-check at midday if the temperature exceeds 95 degrees 
Fahrenheit (F). Leveling should be avoided during hot temperatures. 

• Perform a C-check at about the same time each day. Atmospheric 
refraction varies during the day and introduces systematic changes to 
theC-factor. 



Error 

in { 
30 m l 



Ae 



Horizontal line 
line oTsight 



j 



Horizontal line 



y-^-_- 

T. ~ - — _ Ae i 
Llr >e of sight """ ~~ ■ 




Station A 



Error 

in 
30 m 



Station B 



30 m (100 ft) 



30 m (100 ft) 



First Setup 



Horizontal line 




Station A 



Error 

in 
60 m 



Station B 



60 m (200 ft) 



LEGEND: 

e = error 



Second Setup 



Figure 7-2. Peg Test 



7-4 Differential Leveling 



FM 3-34.331 



SECTION II - PRECISE LEVELING PROCEDURES 



7-9. Differential-leveling observations area repetitive operation, which due to 
the regimen, often leadtoa misunderstanding of the error sources. Duetothe 
number of small systematic errors that are not discernible from geometric 
checks, it is imperative to adhere to the prescribed procedures. 



RECON 



7-10. The leveling party performs a recon of the level line. Existing BMs 
should be recovered and description/recovery notes prepared. BMs along the 
level line are established according to FGCC standards. At all orders of 
accuracy, the leveling party will verify that the starting BM elevation is 
correct by performing two-way leveling to the closest adjacent BM and back. 
These BMs should be part of the same level-line network that originally 
established them. All members of the leveling party should exercise caution in 
the choice of the route for leveling. High-traffic areas should be avoided, and if 
this is not possible, the leveling party should maintain high visibility at all 
times. Road-guard vests and additional personnel may be necessary to ensure 
the leveling party's safety. The ground over which the leveling progresses 
should be free of characteristics that will introduce anomalous measurements. 
Ground that radiates high refraction or that is soft or uneven should be 
bypassed if possible. Any time that high scintillation is observed between the 
level and the rod, sight distances must be reduced. 



DE DETERMINATION 



7-11. The terms differential leveling, direct leveling, geodetic leveling, and 
spirit leveling all describe the same activity— the determination of DEs by 
direct observation. These terms are used interchangeably in this publication. 
Follow these steps when performing third-order differential leveling: 

Step 1. Determine the C-factor each day (just before leveling begins) and 

immediately following any instance when the level is subjected to an unusual 

shock. Record the results of theC-check and keep them in the project records. 

Step 2. Start and end the leveling on BMs of third-order accuracy or higher. 

Step3. Use three-wire-leveling methods. 

Step 4. Do not make observations closer to the ground than 0.5 meter. Do not 

make observations on the rod higher than the project specifications require. 

Step5. Leapfrog the rods forward. 

Step 6. Observe an even number of setups between the starting and ending 

BMs. 

Step 7. Place the rods in the red-rod-first sequence— rod number 1 or A of a 

matched pair of rods is marked (the foot of the rod is painted or a flagging is 

attached to the rod) to distinguish it from the other rod. The marked rod is 

observed and the readings are recorded first for each setup. 

Step 8. Double-run the sections from the first BM out to the next BM and 

return. 



Differential Leveling 7-5 



FM 3-34.331 



Step 9. Determine the maximum allowable disclosure. It will be the lesser of 
the following computed values: 

• Twelve millimeters times the square root of the shorter-distance run 
between the BMs in kilometers. 

• Twelve millimeters times the square root of the perimeter of the loop 
(front and back runs combined) in kilometers. 

Step 10. Ensure that any action not specified above complies with the 
specifications set forth by the FGCC. 

Step 11. Ensure compliance with steps 1 through 10 at all times unless the 
customer sets forth specific methodology, standards, or specifications for 
performing the differential leveling in the request for survey support. 



FIELD-PARTY COMPOSITION 



7-12. The field party consists of four members— two rodmen, a level observer, 
and a recorder. The duties of each member are identified as follows: 

• Rodmen. The rodmen hold the level rod; pace the sight distances 
between the instrument and the level rod toensurethat the minimum 
inequalities of the setup and the accumulated sight distances are 
maintained; hold the rod during readings in a plumb and steady 
vertical position using the handles of the rod; pi ace the rod in precisely 
the same position for the backsight as it was for the foresight; carry 
the rod using the handles (not over the shoulder); and ensure that the 
rod face, the sole of the rod, and the circular bubble do not contact the 
ground or receive a sudden shock (the level rod is a precise-survey 
instrument and must be treated as such). 

• Observer. The observer performs the observations, is responsible for 
the care and condition of the instrument and accessories, ensures that 
the maximum sight distance is not exceeded when moving the level 
from the last foresight level rod to the next instrument setup, inspects 
the level tripod to ensure that all parts are secure and adjusted 
properly, deliberately places the level to provide a stable platform, 
carefully levels the instrument and reads the appropriate data, and 
never leaves the geodetic level unattended. 

• Recorder. The recorder is responsible for all documentation during 
the survey; completes all note forms properly; ensures that all 
requirements are satisfied; ensures that calculations and checks are 
performed without errors and expeditiously and that all technical 
specifications have been satisfied; and prepares the description of BMs 
and any supplemental vertical -control points. 



DATA RECORDING 



7-13. Procedures for recording differential-leveling data are the same for all 
orders of accuracy. Differential-leveling data (include the names of the rodmen) 
is recorded on DA Form 5820-R or any other single-sheet recording form 
authorized by the party chief (F igure7-3). After recording the raw 



7-6 Differential Leveling 



FM 3-34.331 



observations to three decimal places, use the following rules to determine the 
mean center-wire reading to four decimal places: 

• If the top interval is LARGER than the bottom, ADD the correction 
factor to the recorded center-wire reading to obtain the mean center- 
wire value to four decimal places. 

• If the top interval is SMALLER than the bottom, SUBTRACT the 
correction factor from the recorded center-wire reading to obtain the 
mean center-wire value to four decimal places. 

7-14. The maximum permissible interval imbalance for third-order 
specification is 3 millimeters. Table7-1, page7-8, shows the correction factors 
for center-wire leveling. 







Three-Wire Leveling 
For use of this form, use FM 3-34.331 ; the proponent agency is TRADOC. 






Project 

Example 


Location 

Fort Belvoir, Virqinia 


Organization 

DMS 




Observer 

SFC JONES 


Recorder 

SGT SMITH 


Instrument 

Wild NA2 - 1234 


Sun 

Warm 


Wind 

Windy 


Weather 
Clear 


From To 

D2 


BASS 


Date 

06 October 86 


Time 

0830 - 0920 


Line or Net 

Training 1 


Page 
no. 2 


No. of 

pas. 4 


Station 


Backsight 
Face of rod 


Mean 


Back 
of rod 


Interval 


Sum of 
intervals 


Foresight 
Face of rod 


Mean 


Back 
of rod 


Interval 


Sum of 
intervals 


Remarks 


























D2 


1201 










2963 














0850 


0850.3 




351 




2623 


2622.3 




340 








0500 






350 


701 


2281 






342 


682 






2551 


0850.3 






701 


7867 


2622.3 






682 






























2657 










0899 














2406 


2406.0 




251 




0638 


0637.7 




261 








2155 






251 


502 


0376 






262 


523 






9769 


3256.3 






1203 


9780 


3260.0 






1205 






























3081 










1361 




r 












2779 


2779.3 




302 




1050 


105 




311 








2478 






301 


603 


0739 




311 


622 






18107 


+6035.6 






1806 




' - J 


4" O.o 






1827 


BASS 


































-4310.0 








1 








1806 






BDE = 


+ 1.7256 














B distance 


3633 














































km 


0.3633 






































































































































































INST OP INT 
1st COMP INT 




FDE = 


-1 .7276 








AE= 0.012 


Vdistance km 




F distance 


0.3302 




BDE- 


+1 .7256 








AE-±0.012 


rJO.3302 
























B distance 


0.3633 




EC = 


-0.0020 








AE > 


±0.0068 








2nd COMP INT 




DA Form 5820-R, AUG 89 







Figure 7-3. Example of Survey Notes for Three-Wire Leveling 



Differential Leveling 7-7 



FM 3-34.331 



Table 7-1. Correction Factors for Center-Wire Leveling 



Difference in Intervals 


Center-Wire Correction Value 


0.000 


0.0000 


0.001 


0.0003 


0.002 


0.0007 


0.003 


0.0010 



C-F ACTOR DETERMINATION 



7-15. The determination of the C-factor may be performed as a part of leveling 
or separately. I n all cases, the C-factor determination must be recorded 
separately from other recordings and must comply with all requirements for 
note keeping. It is desirable to determine the C-factor under the same 
conditions that the leveling will be performed, including the sight distance, 
the slope of the ground, and the elevation of the line of sight above the ground. 

7-16. E nsure that the circular bubble is carefully centered and that the 
observed ends of the bubble in the level vial are in coincidence (when 
applicable) before reading the three wires. If theC-factor is determined during 
thefirst setup of the leveling, perform thefollowing steps: 

Step 1. Observe and record the foresight readings on the C-factor note sheet 
after the regular foresight observations are recorded for the level line. 
Step 2. Position the rear rodman to about 10 meters behind the level. 
Step 3. Observe and record the rear-rod readings on the C-factor note sheet. 
Step 4. Move the level to about 10 meters behind the front rod. 
Step5. Observe and record the front-rod readings on the C-factor note sheet. 
Step 6. Observe and record the rear-rod readings on the C-factor note sheet. 

7-17. The total correction for curvature and refraction (C&R) must be 
determined for each far-rod reading using the distance from the instrument to 
the far rod as the argument. Distances equal the product of the sum of the 
intervals (for a single set of three-wire readings) times the stadia-interval 
factor (SI F). The two corrections for C&R are algebraically added to the sum of 
the mean wire readings for the distant rod. The maximum permissible 
C-factor varies with the SI F . I nstruments with a SI F of 1:100 may not have a 
C-factor of greater than dfl.004. 1 nstruments with a SI F of 1:200 may not have 
a C-factor of greater than dfl.007. I nstruments with a SI F of 1:333 may not 
have a C-factor of greater than ±0.010. If the C-factor is determined to be 
greater than what is permitted for the instrument's SI F, the instrument must 
be adjusted and the C-factor redetermined before performing differential 
leveling. The notes for the C-factor determination become part of the 
administrative notes for the leveling operation. 



7-8 Differential Leveling 



FM 3-34.331 



CENTER-WIRE ADj USTMENT 



7-18. I f the C-factor exceeds the SI F I i mits, a correction to the center wi re 
must be made. Determine this correction by multiplying the total rod interval 
of the last foresight (distant rod) by the computed C-factor. Compute the 
correction to three places to the right of the decimal point and include the 
algebraic sign of the C-factor. The correction to the center wire is algebraically 
added to the last foresight mean wire reading. The result will be the corrected 
center-wire reading. Compute the corrected center-wire reading to three 
places to the right of the decimal point. 

7-19. Follow the manufacturer's manual to adjust the level until the corrected 
center-wire reading is observed on the distant rod. Perform a C-check to 
ensure that the new C-factor is within the acceptable limits. 



SIF DETERMINATION 



7-20. The SIF is required to compute the length (horizontal distance) from the 
stadia intervals and to determine the maximum AE for a level line. The SIF 
must be determined if the reticle (which contains the etched stadia wires) is 
replaced or changed. The notes from the SIF determination become part of the 
records that are kept with the level and the project files. 

7-21. The SIF determination is made by comparing the stadia intervals that 
were observed over a course of known distances. Lay out the course on a 
reasonably level track, roadway, or sidewalk. Place nails or other marks in a 
straight line of measured distances of 25, 35, 45, 55, 65, and 75 meters. Plumb 
the optical zero point of the level over the zero marker on the ground and level 
the instrument. The optical zero point of the level is found in the 
manufacturer's manual. Read the rod at each of the six points and record the 
intervals. Compute the half-wire intervals as a check against erroneous 
readings. Compute the sum of the six interval readings. The SIF is the sum of 
the measured distances (300 meters total), divided by the sum of the six 
interval readings. 

7-22. To check for errors, compute the SI F for each of the six readings and 
divide the measured distance by the total interval readings observed for that 
distance. The average of the six computations will serve as a numerical check. 
A tendency for the six computed values to creep in one direction indicates an 
error in plumbing the optical zero point of the level over the zero point on the 
ground. 



Differential Leveling 7-9 



Chapter 8 
NAVSTAR GPS 

This chapter provides a general overview of the NAVSTAR GPS. The 
NAVSTAR GPS is a passive, satellite-based navigation system that is 
operated and maintained by DOD. Its primary mission is to provide 
passive global positioning/navigation for air-, land-, and sea-based 
strategic and tactical forces. 



SECTION I - GPS OVERVIEW 



8-1. A GPS receiver is a simple range-measurement device. Distances are 
measured between the receiver antenna and the satellites, and the position is 
determined from the intersections of the range vectors. These distances are 
determined by a GPS receiver, which precisely measures the time it takes a 
signal to travel from the satellite to the station. This measurement process is 
similar to that used in conventional-pulsing marine-navigation systems and 
in phase-comparison EDM land-surveying equipment. 

OPERATING AND TRACKING MODES 

8-2. There are two, general operating modes from which GPS-derived 
positions can be obtained— absolute and relative (or differential) positioning. 
Within each of these two modes, range measurements to the satellites can be 
performed by tracking either the phase of the satellite's carrier signal or PRN 
codes that are modulated on the carrier signal. In addition, GPS positioning 
can be performed with the receiver operating in a static or dynamic 
(kinematic) environment. This variety of operational options results in a wide 
range of accuracy levels that can be obtained from the NAVSTAR GPS. 
Accuracies can range from 100 meters down to less than 1 centimeter. 
I ncreasing the accuracy to less than 1 centimeter requires additional 
observation time and can be achieved in real time. The selection of a 
particular GPS operating and tracking mode (for example, absolute, 
differential, code, carrier, static, kinematic, or combinations thereof) depends 
on the user's application. Topographic surveying typically requires differential 
positioning using carrier-phase tracking. Absolute modes are rarely used for 
geodetic surveying except when worldwide reference control is being 
established. 

ABSOLUTE POSITIONING 

8-3. Absolute positioning is the most common military and civil application of 
NAVSTAR GPS for real-time navigation. When operating in this passive, 



NAVSTAR GPS 8-1 



FM 3-34.331 



real-time navigation mode, ranges to NAVSTAR GPS satellites are observed 
by a single receiver positioned on a point for which a position is desired. This 
receiver may be positioned to be stationary over a point (static) or in motion 
(kinematic [such as on a vehicle, aircraft, missile, or backpack]). Two levels of 
absolute-positioning accuracy may be obtained— SPS and PPS. With 
specialized GPS receiving equipment, data-processing refinements, and long- 
term static observations, absolute-positional coordinates can be determined to 
accuracy levels of less than 1 meter. These applications are usually limited to 
worldwide geodetic-reference surveys. 

8-4. The SPS user is able to achieve real-time, 3D (point-positional) absolute 
positioning. The SPS is the GPS signal that DOD authorizes to civil users. 
This level of accuracy is due to the deli berate degradation of theGPS signal by 
DOD for national security reasons. DOD degradation of theGPS signal is 
referred to as selective availability (S/A). DOD has also implemented 
antispoofing (AS), which denies the SPS user the more accurate precision code 
(P-code). 

8-5. Using the PPS requires DOD authorization for a decryption device that is 
capable of deciphering the encrypted GPS signals. Army topographic 
surveyors are authorized users; however, actual use of the equipment has 
security implications. Real-time, 3D absolute-positional accuracies of 16 to 20 
meters are attainable through the PPS. 



DIFFERENTIAL POSITIONING 



8-6. Differential positioning is a process of measuring the differences in 
coordinates between two receiver points, each of which is simultaneously 
observing/measuring satellite code ranges and/or carrier phases from the 
NAVSTAR GPS constellation. This process measures the difference in ranges 
between the satellites and two or more ground observing points. The range 
measurement is performed by a phase-difference comparison, using either the 
carrier or code phase. The basic principle is that the absolute-positioning 
errors at the two receiver points will be about the same for a given instant. 
The resultant accuracy of these coordinate differences is at the meter level for 
code-phase observations and at the centimeter level for carrier-phase 
tracking. These coordinate differences are usually expressed as 3D baseline 
vectors, which are comparable to conventional survey azimuth/distance 
measurements. DGPS positioning can be performed in the static or the 
kinematic mode. 



SYSTEM CONFIGURATION 



8-7. The NAVSTAR GPS consists of three distinct segments— the space 
segment (satellites), the control segment (tracking and monitoring stations), 
and the user segment (air-, land-, and sea-based receivers). 



SPACE SEGMENT 



8-8. The space segment consists of all GPS satellites in orbit. The first 
generation of satellites were Block I or developmental. Several of these 
satellites are still operational. A full constellation of Block II or production 
satellites is now in orbit. The full constellation consists of 24 Block 1 1 



8-2 NAVSTAR GPS 



FM 3-34.331 



operational satellites (21 primary with 3 active on-orbit spares). There are 
four satellites in each of six orbital planes inclined at 55° to the equator. The 
satellites are at altitudes of 10,898 nautical miles and have 11-hour, 
56-minute orbital periods. The three spares are transparent to the user on the 
ground (the user is not able to tell which are operational satellites and which 
are spares). A procurement action for Block MR (replacement) satellites is 
underway to ensure full system performance through the year 2025. 



CONTROL SEGMENT 



8-9. The control segment consists of five tracking stations that are located 
throughout the world (Hawaii, Colorado, Ascension Island, Diego Garcia 
Island, and Kwajalein Island). The information obtained from tracking the 
satellites is used in controlling and predicting their orbits. Three of the 
stations (Ascension, Diego Gracia, and Kwajalein) are used for transmitting 
information back to the satellites. The master control station is located at 
Colorado Springs, Colorado. All data from the tracking stations are 
transmitted to the master control station where they are processed and 
analyzed. Ephemerides, clock corrections, and other message data are then 
transmitted back to the three stations that are responsible for subsequent 
transmittal back to the satellites. The master control station is also 
responsible for the daily management and control of the GPS satellites and 
the overall control segment. 

USER'S SEGMENT 

8-10. The user's segment represents the ground-based receiver units that 
process the satellite signals and arrive at a user's position. This segment 
consists of both military and civil activities for an unlimited number of 
applications in a variety of air-, land-, and sea-based platforms. 

BROADCAST FREQUENCIES AND CODES 

8-11. Each NAVSTAR satellitetransmits signals on two L-band frequencies 
(designated as LI and L2). The LI carrier frequency is 1,575.42 megahertz 
and has a wavelength of about 19 centimeters. The L2 carrier frequency is 
1,227.60 megahertz and has a wavelength of about 24 centimeters. The LI 
signal is modulated with a P-code and a coarse-acquisition code (C/A-code). 
The L2 signal is modulated with a P-code only. Each satellite carries precise 
atomic clocks to generate the timing information needed for precise 
positioning. A navigation message is also transmitted on both frequencies. 
This message contains ephemerides, clock corrections and coefficients, the 
health and status of satellites, almanacs of all GPS satellites, and other 
information. 

PSEUDORANDOM NOISE 

8-12. Modulated C/A- and P-codes are referred to as PRN codes. These PRN 
codes are actually a sequence of very precise "time marks" that permit the 
ground receivers to compare and compute the time of transmission between a 
satellite and a ground station. The range to the satellite can be derived from 
this transmission time. This is the basis behind GPS range measurements. 



NAVSTAR GPS 8-3 



FM 3-34.331 



C/A-code pulse intervals are about every 300 meters in range. The more 
accurate P-code pulse intervals are about every 30 meters. 



PSEUDORANGES 



SPS 



PPS 



8-13. A pseudorange is the time delay between the satellite clock and the 
receiver clock, as determined from C/A- or P-code pulses. This time difference 
equates to the range measurement but is called a pseudorange since at the 
time of the measurement, the receiver clock is not synchronized to the 
satellite clock. In most cases, an absolute real-time, 3D navigational position 
can be obtained by observing at least four simultaneous pseudoranges. 



8-14. The SPS uses the less precise C/A-code pseudoranges for real-time GPS 
navigation. Due to deliberate DOD degradation of the C/A-code accuracy, 
100 meters in horizontal and 156 meters in vertical accuracy levels result. 
These accuracy levels are adequate for most civil applications where only 
approximate real-time navigation is required. 



8-15. The PPS is the fundamental military real-time navigational use of the 
GPS. Pseudoranges are obtained using the higher pulse rate (higher accuracy) 
P-code on both frequencies (LI and L2). Real-time, 3D accuracies at the 
16-meter level can be achieved with the PPS. The P-code is encrypted to 
prevent unauthorized civil or foreign use. This encryption requires a special 
decryption code to obtain this 16-meter accuracy. 



CARRIER-PHASE MEASUREMENTS 



8-16. Carrier -frequency tracking measures the phase differences between the 
Doppler-shifted satellite and receiver frequencies. The phase differences are 
continuously changing due to the changing satellite earth-orbit geometry. 
However, such effects are resolved in the receiver and subsequent data 
postprocessing. When carrier-phase measurements are observed and 
compared between two stations (differential mode), 3D baseline-vector 
accuracy (below the centimeter level) between the stations is attainable. New 
receiver technology and processing techniques have allowed for carrier-phase 
measurements to be used in real-time centimeter positioning. 



BROADCAST EPHEMERIS DATA 



8-17. Each NAVSTAR GPS satellite periodically broadcasts data concerning 
clock corrections, system/satellite status and, most critically, its position or 
ephemeris data. There are two basic types of ephemeris data— broadcast and 
precise. 



BROADCAST EPHEMERIDES 



8-18. Broadcast ephemerides are predicted satellite positions that are 
broadcast within the navigation message, which is transmitted from the 
satellites in real time. The ephemerides can be acquired in real time by a 



8-4 NAVSTAR GPS 



FM 3-34.331 



receiver that is capable of acquiring either the C/A- or P-code. The broadcast 
ephemerides are computed by using the past tracking data of the satellites. 
The satellites are tracked continuously by the monitor stations to obtain more 
recent data to use for orbit predictions. The data are analyzed by the master 
control station, and new parameters for the satellite orbits are transmitted 
back to the satellites. This upload is performed daily and the newly predicted 
orbital elements are transmitted every hour by the navigational message. 
Broadcast ephemerides are adequate to obtain needed accuracies for most 
survey applications. 



PRECISE EPHEMERIDES 



8-19. Precise ephemerides are based on actual tracking data that are 
postprocessed to obtain more accurate satellite positions. These ephemerides 
are delayed for processing but are more accurate than the broadcast 
ephemerides because they are based on actual tracking data and not predicted 
data. Civilian users can obtain this information from the NGS or private 
sources that maintain their own tracking networks and provide the 
information for a fee. 



SECTION II - ABSOLUTE POSITIONING 



8-20. Absolute positioning involves the use of only one passive receiver at one 
station location to collect data from multiple satellites to determine the 
station's location. It is not sufficiently accurate for precise surveying and 
positioning uses. However, it is the most widely used GPS-positioning method 
for real-time navigation and location. 



ABSOLUTE-POSITIONING ACCURACIES 



8-21. Absolute-positioning accuracies are dependent on the user's 
authorization. The SPS user can obtain real-time, 3D accuracies of 
100 meters. The lower level of accuracies achievable using the SPS is due to 
the intentional degradation of the GPS signal by DOD S/A. The PPS user 
(usually a DOD-approved user) can use a decryption device to achieve a 3D 
accuracy in the range of 10 to 16 meters with a single-frequency receiver. 
Accuracy to less than 1 meter can be obtained from absolute GPS 
measurements when special equipment and postprocessing techniques are 
employed. 

8-22. By using broadcast ephemerides, the user is able to use pseudorange 
values in real time to determine absolute-point positions with an accuracy of 
between 3 meters in the best of conditions and 80 meters in the worst of 
conditions. By using postprocessed (precise) ephemerides, the user can expect 
absolute point positions with an accuracy of near 1 meter in the best of 
conditions and 40 meters in the worst of conditions. 



PSEUDORANGING 



8-23. When a GPS user performs a GPS navigational solution, only an 
approximate range (or pseudorange) to selected satellites is measured. I n 



NAVSTARGPS 8-5 



FM 3-34.331 



order to determine the user's precise GPS location, the known range to the 
satellite and the position of those satellites must be known. By 
pseudoranging, the GPS user measures an approximate distance between the 
antenna and the satellite without any corrections for errors in 
synchronization between the clock of the transmitter and the clock of the 
receiver. This measurement correlates by correlation of a satellite- 
transmitted code and a reference code that is created by the receiver. The 
distance the signal has traveled is equal to the velocity of the transmission of 
the satellite multiplied by the elapsed time of transmission. The satellite- 
signal velocity changes that are due to tropospheric and ionospheric 
conditions must be considered. 

8-24. The accuracy of the positioned point is a function of the range- 
measurement accuracy and the geometry of the satellites (reduced to 
spherical intersections with the earth's surface). A description of the 
geometrical magnification of uncertainty in a G PS-determined point position 
isthedilution of precision (DOP). Repeated and redundant range observations 
will generally improve range accuracy. However, the DOP remains the same. 
I n a static mode (the GPS antenna stays stationary), range measurements to 
each satellitecan be continuously remeasured over varying orbital locations of 
the satel I ite(s). The varying satellite orbits cause varying positional 
intersection geometry. In addition, simultaneous range observations to 
numerous satellites can be adjusted using weighting procedures that are 
based on the elevation and the pseudorange-measurement reliability. 

8-25. Four pseudorange observations are needed to resolve a GPS 3D 
position. Three pseudorange observations are needed for a two-dimensional 
(2D) (horizontal) location. There are often more than four pseudorange 
observations due to the need to resolve the clock biases contained in both the 
satellite and the ground-based receiver. I n computing the X, Y, and Z 
coordinates of a point, a fourth unknown parameter (clock bias) must also be 
included in the solution. 

ABSOLUTE-POSITIONING ERROR SOURCES 

8-26. There are numerous sources of measurement errors that influence GPS 
performance. The sum of all systematic errors or biases contributing to the 
measurement error is referred to as a range bias. The observed GPS range 
(without removal of biases) is referred to as a biased range or pseudorange. 
Principal contributors to the final range error that also contribute to overall 
GPS error areephemeris error, satellite-clock and electronics inaccuracies, 
tropospheric and ionospheric refraction, atmospheric absorption, receiver 
noise, and multipath effects. Other errors include those induced by DOD S/A 
and AS. I n addition to these major errors, the GPS also contains random 
observation errors (such as unexplainable and unpredictable time variation). 
These errors are impossible to model and correct. The following paragraphs 
discuss errors associated with absolute G PS-positioning modes. Many of these 
errors are either eliminated or significantly minimized when the GPS is used 
in a differential mode, because the same errors are common to both receivers 
during simultaneous observing sessions. 



8-6 NAVSTARGPS 



FM 3-34.331 



EPHEMERIS ERRORS AND ORBIT PERTURBATIONS 

8-27. Satellite-ephemeris errors are errors in the prediction of a satellite's 
position, which may then be transmitted to the user in the satellite data 
message. Ephemeris errors are satellite dependent and are very difficult to 
correct completely and compensate for, because the forces acting on the 
predicted orbit of a satellite are difficult to measure directly. The previously 
stated accuracy levels are subject to the equipment's condition and 
performance. Ephemeris errors produce equal error shifts in the calculated 
absolute-point positions. 

CLOCK STABILITY 

8-28. The GPS relies very heavily on accurate time measurements. GPS 
satellites carry rubidium and cesium time standards that are usually accurate 
to 1 part in 10 trillion and 1 part in 100 trillion, respectively, while most 
receiver clocks are actuated by a quartz standard accurate to 1 part in 100 
million. A time offset is the difference between the time as recorded by the 
satellite clock and the time recorded by the receiver. A range error that is 
observed by the user as a result of time offsets between the satellite and 
receiver clock is a linear relationship and can be approximated. 

8-29. Unpredictable transient situations that produce high-order departures 
in clock time can be stored for short periods of time. I n a plane survey, 
departure is defined as the difference between the castings of the two ends of 
the line, which may be either plus or minus. Predictable time drift of the 
satellite clocks is closely monitored by ground-control stations. Through close 
monitoring of the time drift, the ground-control stations are able to determine 
second-order polynomials that accurately model the time drift. These second- 
order polynomials, determined to model the time drift, are included in the 
broadcast message in an effort to keep this drift to within 1 millisecond. The 
time synchronization between the GPS satellite clocks is kept to within 
20 nanoseconds through the broadcast -clock corrections as determined by the 
ground-control stations and the synchronization of GPS standard time to the 
universal time, coordinated (UTC) to within 100 nanoseconds. Random time 
drifts are unpredictable, thereby making them impossible to model. 

8-30. GPS receiver-clock errors can be modeled in a manner similar toGPS- 
satel lite-clock errors. In addition to modeling the satellite-clock errors and in 
an effort to remove them, an additional satellite should be observed during 
operation to solve for an extra clock offset parameter along with the required 
coordinate parameters. This procedure is based on the assumption that the 
clock bias is independent at each measurement epoch. Rigorous estimation of 
the clock terms is more important for point positioning than for differential 
positioning. Many of the clock terms cancel each other when the position 
equations are formed from observations during a differential-survey session. 

IONOSPHERIC DELAYS 

8-31. GPS signals are electromagnetic signals and as such are nonlinearly 
dispersed and refracted when transmitted through a highly charged 
environment I ike the ionosphere. Dispersion and refraction of the GPS signal 
are referred to as ionospheric range effects, because dispersion and refraction 



NAVSTARGPS 8-7 



FM 3-34.331 



of the signal result in an error in the GPS range value. Ionospheric range 
effects are frequency dependent. 

8-32. The error effect of ionosphere refraction on GPS range values is 
dependent on sunspot activity, the time of day, and satellite geometry. GPS 
operations conducted during periods of high sunspot activity or with satellites 
near the horizon produce range results with the most amount of ionospheric 
error. GPS operations conducted during periods of low sunspot activity, 
during the night, or with a satellite near the zenith will produce range results 
with the least amount of ionospheric error. 

8-33. Resolution of ionospheric refraction can be accomplished by using a 
dual-frequency receiver (a receiver that can simultaneously record both LI 
and L2 frequency measurements). During a period of uninterrupted 
observation of the LI and L2 signals, these signals can be continuously 
counted and differenced. The resultant difference shows the variable effects of 
the ionosphere delay on the GPS signal. Single-frequency receivers used to 
determine an absolute or differential position typically rely on ionospheric 
models that predict the effects of the ionosphere. Recent efforts have shown 
that significant ionospheric-delay removal can be achieved using single- 
frequency receivers. 



TROPOSPHERIC DELAYS 



8-34. GPS signals in the L-band level are refracted and not dispersed by the 
troposphere. Tropospheric conditions that cause refraction of the GPS signal 
can be modeled by measuring the dry and wet components. 



MULTIPATH EFFECTS 



8-35. Multipath describes an error that affects positioning and occurs when 
the signal arrives at the receiver from more than one path. M ultipath 
normally occurs near large reflective surfaces, such as a building or structure 
with a reflective surface, a chain-link fence, or antenna arrays. Multipath is 
caused by the reflection of the GPS signal off of a nearby object, which 
produces a false signal at the GPS antenna. GPS signals received as a result 
of multipath give inaccurate GPS positions when processed. Newer receiver 
and antenna designs and thorough mission planning can minimize multipath 
effects as an error source. The averaging of GPS signals over a period of time 
can also reduce multipath effects. 



RECEIVER NOISE 



S/AAND AS 



8-36. Receiver noise includes a variety of errors associated with the ability of 
the GPS receiver to measure a finite time difference. These errors include 
signal processing, clock/signal synchronization and correlation procedures, 
receiver resolution, and signal noise. 



8-37. S/A purposely degrades the satellite signal to create position errors by 
dithering the satellite clock and offsetting the satellite orbits. The effects of S/A 
can be eliminated by using differential techniques. AS is implemented by 
interchanging the P-code with a classified, encrypted P-code called a Y-code. 



8-8 NAVSTARGPS 



FM 3-34.331 



This denies users who do not possess an authorized decryption device. 
Manufacturers of civil GPS equipment have developed techniques, such as 
squaring or cross correlation, to make use of the P-code when it is encrypted. 



USER EQUIVALENT RANGE ERROR 



8-38. The previously described error sources or biases are principal 
contributors to the overall GPS range error. This total error budget is often 
summarized as the user equivalent range error (U ERE ). As mentioned 
previously, errors can be removed or at least effectively suppressed by 
developing models of their functional relationships in terms of various 
parameters that can be used as a corrective supplement for the basic GPS 
information. Differential techniques also eliminate many of these errors. 
Table8-1 lists significant sources for errors and biases and correlates them to 
the segment source. 

Table 8-1. GPS Range-Measurement Accuracy 



Segment 
Source 


Error Source 


Absolute Positioning 


Differential 
Positioning 
(P-code) (m) 


C/A-code 
Pseudorange (m) 


P-code 
Pseudorange (m) 


Space 


Clock stability 


3.0 


3.0 


Negligible 


Orbit 
perturbations 


1.0 


1.0 


Negligible 


Other 


0.5 


0.5 


Negligible 


Control 


Ephemeris 
predictions 


4.2 


4.2 


Negligible 


Other 


0.9 


0.9 


Negligible 


User 


Ionosphere 


3.5 


2.3 


Negligible 


Troposphere 


2.0 


2.0 


Negligible 


Receiver noise 


1.5 


1.5 


1.5 


Multipath 


1.2 


1.2 


1.2 


Other 


0.5 


0.5 


0.5 


IcUERE 


±12.1 


±6.5 


±2.0 



ACCURACIES 



8-39. The absolute value of range accuracies obtainable from the GPS are 
largely dependent on which code (C/A or P) is used to determine positions. 
These range accuracies (for example, UERE), when coupled with the 
geometrical relationships of the satellites during the position determination 
(for example, DOP), result in a 3D ellipsoid that depicts uncertainties in all 
three coordinates. Given the changing satellite geometry and other factors, 



NAVSTARGPS 8-9 



FM 3-34.331 



DOP 



GPS accuracy is time/location dependent. Error propagation techniques are 
used to define nominal accuracy statistics for a GPS user. 



8-40. The final positional accuracy of a point (determined by using absolute 
GPS-S techniques) is directly related to the geometric strength of the 
configuration of satellites observed during the survey session. GPS errors 
resulting from satellite-constellation geometry can be expressed in terms of 
DOP. In mathematical terms, DOP is a scalar quantity used in an expression 
of a ratio of the positioning accuracy. It is the ratio of the standard deviation 
of one coordinate to the measurement accuracy. DOP represents the 
geometrical contribution of a certain scalar factor to the uncertainty (for 
example, standard deviation) of a GPS measurement. DOP values are a 
function of the diagonal elements of the covariance matrices of the adjusted 
parameters for the observed GPS signal. DOP values are used in point 
formulations and determinations. DOP is a scalar quantity of the contribution 
of the configuration of satellite-constellation geometry to the GPS accuracy. 
DOP can also be a measure of the strength of the satellite-constellation 
geometry. The more satellites that can be observed and used in the final 
solution, the better the solution. Since DOP can be used as a measure of 
geometrical strength, it can also be used to selectively choose four satellites in 
a particular constellation that will provide the best solution. 



Geometric DOP 



Positional DOP 



8-41. The main form of DOP used in absolute GPS positioning is the 
geometric DOP (GDOP). GDOP is a measure of accuracy in a 3D position and 
time. The final positional accuracy equals the actual range error multiplied by 
theGDOP. 



8-42. Positional DOP (PDOP) is a measure of the accuracy in 3D position. The 
PDOP values are generally developed from satellite ephemerides before 
conducting a survey. When developed before a survey, PDOP can be used to 
determine the adequacy of a particular survey schedule. This is valid for 
rapid-static or kinematic surveys but is less valid for a long-duration static 
survey. 

8-43. PDOP represents position recovery at an instant in time and is not 
representative of a whole session of time. A PDOP error is generally given in 
units of meters of error per 1-meter error in a pseudorange measurement. 
When using pseudorange techniques, PDOP values in the range of 4 to 5 
meters of error per 1-meter error are considered very good, while PDOP 
values greater than 10 meters of error per 1-meter error are considered very 
poor. For static surveys, it is generally desirable to obtain GPS observations 
during a time of rapidly changing GDOP or PDOP. 

8-44. When the values of PDOP or GDOP are viewed over time, peak or high 
values (greater than 10 meters of error per 1-meter error) can be associated 
with satellites in a constellation of poor geometry. The higher the PDOP or 
GDOP, the poorer the solution for that instant in time. This is critical in 



8-10 NAVSTARGPS 



FM 3-34.331 



Horizontal DOP 



Vertical DOP 



determining the acceptability of real-time navigation and photogrammetric 
solutions. Poor geometry can be the result of satellites orbiting near each 
other or being in thesame plane or at similar elevations. 



8-45. Horizontal DOP (HDOP) is a measurement of the accuracy in a 2D 
horizontal position. The HDOP statistic is most important in evaluating 
GPS-Ss intended for horizontal control. HDOP is the RMS error determined 
from the final variance-covariance matrix divided by the standard error of the 
range measurements. HDOP roughly indicates the effects of satellite-range 
geometry on a resultant position. 



8-46. Vertical DOP (VDOP) is a measurement of the accuracy in the standard 
deviation of a vertical height. Table8-2 indicates generally accepted DOP 
values for a baseline solution. 

Table 8-2. Acceptable DOP Values 



Measurement 


DOP Value 


Comment 


GDOP and 
PDOP 


Less than 1 meters of error per 1 - 
meter error (optimally 4 to 5 meters 
of error per 1 -meter error) 


In static GPS surveying, it is desirable to have a 
GDOP/PDOP that changes during the time of the 
GPS-S session. 

The lower the GDOP/PDOP, the better the 
instantaneous point-position solution. 


HDOP and 
VDOP 


2 meters of error per 1 -meter error 


This DOP value results in the best constellation of 
four satellites. 



ACCURACY COMPARISONS 



8-47. It is important that G PS-accuracy measures clearly identify the statistic 
from which they were derived. A 100-meter or positional variance-covariance 
matrix is meaningless unless it is identified as being either one dimensional 
(ID), 2D, or 3D, along with the applicable probability level. For example, a 
PPS 16-meter 3-deviation accuracy is, by definition, a spherical error probable 
(SEP) (50 percent). This 16-meter SEP equates to a 28-meter 3D, 95 percent 
confidence spheroid. If transformed to 2D accuracy, the SEP equates roughly 
to a 10-meter circular error probable (CEP), a 12-meter root-mean-square 
(RMS), a 2-meter 2-deviation RMS, or a 36-meter 3-deviation RMS. Table8-3 
shows additional information on GPS-measurement statistics. In addition, 
absolute GPS point-positioning accuracies are defined relative to an earth- 
centered coordinate system/datum. This coordinate system will differ 
significantly from local or construction datums. Nominal GPS accuracies may 
also be published as design or tolerance limits, and accuracies achieved can 
differ significantly from these values. 



NAVSTARGPS 8-11 



FM 3-34.331 



Table 8-3. Representative GPS Error-Measurement Statistics for Absolute-Point Positioning 



Error-Measure Statistic 


Probability 

% 


Relative 

Distance 

(ft) 1 


GPS Precise- 
Positioning Service 

(m) 2 


GPS Standard- 
Positioning Service 

(m) 2 


1D Measures 


On or oe 


ou 


On or a E 


ou 


Probable error 


50.00 


0.6745 a 


±4.0 


±9.0 


±24.0 


±53.0 


Average error 


57.51 


0.7979 o 


±5.0 


±11.0 


±28.0 


±62.0 


1o standard error/deviation 3 


68.27 


1.0000 o 


±6.3 


±13.8 


±35.3 


±78.0 


90% probability (map accuracy standard) 


90.00 


1 .6450 a 


±10.0 


±23.0 


±58.0 


±128.0 


95% probability/confidence 


95.00 


1 .9600 a 


±12.0 


±27.0 


±69.0 


±153.0 


2o standard error/deviation 


95.45 


2.0000 a 


±12.6 


±27.7 


±70.7 


±156.0 


99% probability/confidence 


99.00 


2.5760 a 


±16.0 


±36.0 


±91.0 


±201.0 


3o standard error (near certainty) 


99.73 


3.0000 o 


±19.0 


±42.0 


±106.0 


±234.0 


2D Measures 4 


Circular Radius 


Circular Radius 


1o standard error circle 5 


39.00 


1 .0000 c c 


6.0 


35.0 


CEP 6 


50.00 


1.1770 o c 


7.0 


42.0 


1-deviation RMS (1DRMS) 3 ' 7 


63.00 


1.4140 g c 


9.0 


50.0 


Circular map accuracy standard 


90.00 


2.1460 g c 


13.0 


76.0 


95% 2D positional confidence circle 


95.00 


2.4470 g c 


15.0 


86.0 


2-deviation RMS (2DRMS) 8 


98.00 


2.8300 a c 


17.8 


100.0 


99% 2D positional confidence circle 


99.00 


3.0350 a c 


19.0 


107.0 


3.5a circular near-certainty error 


99.78 


3.5000 a c 


22.0 


123.0 


3-deviation RMS (3DRMS) 


99.90 


4.2400 g c 


27.0 


150.0 


3D Measures 


Spherical Radius 


Spherical Radius 


1o spherical standard error 9 


19.90 


1 .0000 o s 


9.0 


50.0 


SEP 10 


50.00 


1 .5400 o s 


13.5 


76.2 


Mean radial spherical error (MRSE) 11 


61.00 


1 .7300 a s 


16.0 


93.0 


90% spherical accuracy standard 


90.00 


2.5000 o s 


22.0 


124.0 


95% 3D confidence spheroid 


95.00 


2.7000 o s 


24.0 


134.0 


99% 3D confidence spheroid 


99.00 


3.3700 o s 


30.0 


167.0 


Spherical near-certainty error 


99.89 


4.0000 o s 


35.0 


198.0 



8-12 NAVSTARGPS 



FM 3-34.331 



Table 8-3. Representative GPS Error-Measurement Statistics for Absolute-Point Positioning 

(continued) 



Error-Measure Statistic 





Relative 


GPS Precise- 


GPS Standard- 


Probability 


Distance 


Positioning Service 


Positioning Service 


% 


(ft) 1 


(m) 2 


(m) 2 



1 Valid for 2- and 3-deviation only if o>j = a E = o\j- (°minimum/0 max imum) 9 enerallv must be >0.2. Relative distance used 

unless otherwise indicated. 

2 Representative accuracy based on 1990 Federal Radio Navigation Plan (FRNP) simulations for PPS and SPS (FRNP 

estimates shown in bold italics) and that o N » o E . SPS may have significant short-term variations from these nominal 

values. 

3 Statistic used to define USACE hydrographic survey depth and positioning criteria. 

4 The 1990 FRNP also proposes SPS maintain, at minimum, a 2D confidence of 300 meters @ 99.99 percent 

probability. 

5 a c =■ 0.5 (a N + o E ) — approximates standard error ellipse. 

6 CEP =• 0.589 (a N + o E ) = 1.18 o c . 

7 1DRMS = (o N 2 + a E 2 ) K . 

8 2DRMS =■ 2 (a N 2 + a E 2 f. 

9 a s =• 0.333 (a N + a E + a u ). 

10 SEP = 0.513 (a N + a E + au). 

11 MRSE - (a N 2 + a E 2 + a u 2 f- 

LEGEND: 

a c = approximate standard error ellipse 

o s = nominal standard error 

NOTES: 

1. Most commonly used statistics are shown in bold-face type. 

2. Estimates are not applicable to differential GPS positioning. Circular/spherical error radii do not have ± signs. 

3. Absolute positional accuracies are derived from GPS-simulated user range errors/deviations and the resultant 
geocentric-coordinate solution (X-Y-Z) covariance matrix, as transformed to a local datum (N-E-U or <I>-X,-h). GPS 
accuracy will vary with GDOP and other numerous factors at time(s) of observation. The 3D covariance matrix yields 
an error ellipsoid. Transformed ellipsoidal dimensions given (for example, o N <j e or oy) are only average values 
observed under nominal GDOP conditions. Circular (2D) and spherical (3D) radial measures are only approximations 
to this ellipsoid, as are probability estimates. 



ROOT -MEAN-SQUARE ERROR MEASURES 



8-48. Two-dimensional GPS positional accuracies are normally estimated 
using a RMS radial-error statistic. A 1-sigma (sigma is denoted by a) RMS 
error equates to the radius of a circle with a 63 percent probability that the 
position is within the circle. A circle of twice this radius (2a) represents about 
a 97 percent probability. This 97 percent probability circle, or 2a RMS, is the 
most common positional-accuracy statistic used in GPS surveying. I n some 
instances, a 3o RMS (99 or more percent probability) is used. This RMS error 
statistic is also related to the positional variance-covariance matrix. An RMS 
error statistic represents the radius of a circle and, therefore, is not preceded 
by a + sign. 



PROBABLE ERROR MEASURES 



8-49. Three-dimensional GPS-accuracy measurements are commonly 
expressed by SEP. The SEP represents the radius of a sphere with a 
50 percent confidence or probability level. This spheroid radial measure only 
approximates the actual 3D ellipsoid representing the uncertainties in the 



NAVSTARGPS 8-13 



FM 3-34.331 



geocentric coordinate system. In 2D horizontal positioning, a CEP statistic is 
commonly used, particularly in military targeting. The CEP represents the 
radius of a circle containing a 50 percent probability of position confidence. 



SECTION III - DIFFERENTIAL PRECISE POSITIONING 



8-50. Absolute positioning does not provide the accuracies needed for most 
survey-control projects due to existing and induced errors. To eliminate the 
errors and obtain higher accuracies, the GPS can be used in a differential- 
positioning mode. The terms "relative" and "differential" used throughout this 
manual have similar meaning. Relative is used when discussing one thing in 
relation to another. Differential is used when discussing the method of 
positioning one thing in relation to another. Differential positioning requires 
that at least two receivers be set up at two stations (usually one is known) to 
collect satellite data simultaneously to determine coordinate differences. This 
method positions the two stations relative to each other (hence the term 
relative positioning) and can provide the accuracies required for basic land 
surveying. 

CODE-PSEUDORANGE TRACKING 

8-51. Differential positioning (using code pseudoranges) is performed 
similarly to code-pseudorange tracking for absolute positioning. Code- 
pseudorange tracking effectively eliminates or minimizes some of the major 
uncertainties. This pseudorange process results in the absolute coordinates of 
the user on the earth's surface. E rrors in range are directly reflected in 
resultant coordinate errors. Differential positioning is not as concerned with 
the absolute position of the user as with the relative difference between two 
user positions, which are simultaneously observing the same satellites. Since 
errors in the satellite position and atmospheric-delay estimates are effectively 
the same at both receiving stations, the errors cancel each other to a large 
extent. 

8-52. For example, if the true pseudorange distance from a known control 
point to a satellite is 100 meters and the observed or measured pseudorange 
distance is 92 meters, then the pseudorange error or correction is 8 meters for 
that particular satellite. A pseudorange correction (PRC) can be generated for 
each satellite being observed. If a second receiver is observing at least four of 
the same satellites and is within a reasonable distance, it can use these PRCs 
to obtain a relative position to the known control point si nee the errors will be 
similar. Thus, the relative distance (coordinate difference) between the two 
stations is reasonably accurate regardless of poor absolute coordinates. In 
effect, the GPS-observed baseline vectors are no different from azimuth/ 
distance observations. As with a total station, any type of initial-coordinate 
reference can be input to start the survey. 

8-53. The GPS coordinates will not coincide with the user's local-project 
datum coordinates. Since differential -survey methods areconcerned only with 
relative coordinate differences, disparities with the global reference system 
used by the NAVSTAR GPS are not significant for topographic purposes. 
Therefore, GPS coordinate differences can be applied to any type of I oca I - 
project reference datum (for example, NAD 27 or NAD 83). 



8-14 NAVSTAR GPS 



FM 3-34.331 



CARRIER-PHASE TRACKING 



8-54. Differential positioning (using carrier phases) uses a formulation of 
pseud oranges. The process becomes more complex when the carrier signals 
are tracked so that range changes are measured by phase resolution. I n 
carrier-phase tracking, an ambiguity factor is added, which must be resolved 
to obtain a derived range. Carrier-phase tracking provides for a more accurate 
range resolution due to the short wavelength (about 19 centimeters for LI and 
24 centimeters for L2) and the ability of a receiver to resolve the carrier phase 
down to about 2 millimeters. This technique has primary application to 
engineering, topographic, and geodetic surveying and may be employed with 
either static or kinematic surveys. There are several techniques that use the 
carrier phase to determine a station's position. These include static, rapid- 
static, kinematic, stop-and-go kinematic, pseudokinematic, and on-the-fly 
(OTF) kinematic/RTK. Table8-4 lists these techniques and their required 
components, applications, and accuracies. 

Table 8-4. Carrier-Phase Tracking 



Technique 


Requirements 


Applications 


Accuracy 


Static 
(postprocessing) 


L1 or L1/L2GPS receiver 

386/486 computer for 
postprocessing 

45-minute to 1-hour minimum 
observation time 1 


Control surveys 
(high-accuracy) 


Subcentimeter 
level 


Rapid static 
(postprocessing) 


L1/L2GPS receiver 

5- to 20-minute observation time 1 


Control surveys 
(medium- to high- 
accuracy) 


Subcentimeter 
level 


Kinematic 2 
(postprocessing) 


L1 GPS receiver with kinematic 
survey option 

386/486 PC for postprocessing 


Continuous topographic 
surveys 

Location surveys 


Centimeter level 


Stop-and-go kinematic 2 
(postprocessing) 


L1 GPS receiver 

386/486 PC for postprocessing 


Control surveys 
(medium-accuracy) 


Centimeter level 


Pseudokinematic 2 
(postprocessing) 


L1 GPS receiver 

386/486 computer for 
postprocessing 


Control surveys 
(medium-accuracy) 


Centimeter level 


OTF/RTK kinematic 3 
(real-time or 
postprocessing) 


Real-time processing: 
Internal or external processor (a PC 
with dual communication ports) 
Minimum 4800 baud radio/modem 
data-link set 

Postprocessing: 
L1/L2 GPS receiver 
386/486 PC 


Hydro surveys 
(real-time, high-accuracy) 

Location surveys 

Control surveys 
(medium-accuracy) 

Photo control surveys 

Continuous topographic 
surveys 


Subdecimeter 
level 


1 Dependent on the satellite constellation and the number of satellites in view. 

2 An initialization period is required, and loss of satellite lock is not tolerated. 

3 No static initialization is necessary, integers are gained while moving, and loss of satellite lock is 
tolerated. 



NAVSTARGPS 8-15 



FM 3-34.331 



STATIC 



8-55. Static surveying is the most widely used differential technique for 
control and geodetic surveying. It involves long observation times (1 to 2 
hours, depending on the number of visible satellites) to resolve the integer 
ambiguities between the satellite and the receiver. Accuracies of less than a 
centimeter can be obtained from this technique. 



RAPID STATIC 



KINEMATIC 



8-56. Rapid-static surveying measures baselines and determines positions in 
the centimeter level with a short observation time (5 to 20 minutes). The 
observation time is dependent on the length of the baseline and the number of 
visible satellites. When moving from one station to the next, loss of satellite 
lock (also referred to as loss of lock) can occur since each baseline is processed 
independently. 



8-57. Kinematic surveying allows the user to rapidly and accurately measure 
baselines, while moving from one point to the next. The data are collected and 
postprocessed to obtain accurate positions to the centimeter level. This 
technique permits only partial loss of lock during observation and requires a 
brief period of static initialization. The OTF technology, both real-time and 
postprocessed, could eventually replace standard kinematic procedures for 
short baselines. 



STOP-AND-GO KINEMATIC 



8-58. Stop-and-go kinematic surveying involves collecting data for a few 
minutes (1 to 2 minutes) at each station (after a period of initialization) to 
gain the integers. This technique does not allow for loss of lock during the 
survey. If loss of lock occurs, a new period of initialization must take place. 
This technique can be performed with two fixed or known stations to provide 
redundancy and improve accuracy. 



PSEUDOKINEMATIC 



OTF/RTK 



8-59. Pseudokinematic surveying is similar to standard kinematic and static 
procedures combined. The differences are no static initialization, a longer 
period of time at each point (about 1 to 5 minutes) (each point must be 
revisited after about one hour), and loss of lock is acceptable. Pseudokinematic 
surveying is less acceptablefor establishing baselines, because the positional 
accuracy is less than that for kinematic or rapid-static surveying. 



8-60. OTF/RTK kinematic surveying uses GPS technology to allow 
positioning to less than a decimeter in real time. This technique determines 
the integer number of carrier wavelengths from the GPS antenna to the GPS 
satellite, transmitting them while in motion and without static initialization. 
The basic concept behind OTF/RTK kinematic surveying is kinematic 
surveying without static initialization (integer initialization is performed 
while moving) and allowances for loss of lock. Other GPS techniques that can 



8-16 NAVSTARGPS 



FM 3-34.331 



achieve this kind of accuracy require static initialization while the user is not 
moving and do not allow for loss of lock while in motion. 



VERTICAL MEASUREMENTS 



8-61. The GPS is not recommended for third-order or higher vertical-control 
surveys or as a substitute for standard differential leveling. It is practical for 
small-scale topographic mapping or similar projects. 



ELEVATION DETERMINATION 



8-62. The height component of GPS measurements is the weakest plane 
because of the orbital geometry of the X, Y, and Z position determination. 
Thus, G PS-ellipsoidal height differences are usually less accurate than the 
horizontal components. G PS-derived elevation differences do not meet third- 
order standards (as obtained by using conventional levels) and must be used 
with caution. 



TOPOGRAPHIC MAPPING 



8-63. GPS positioning, whether in the absolute or differential positioning 
mode, can provide heights (or height differences) of surveyed points. The 
height or height difference obtained from the GPS is in terms of height above 
or below the WGS-84 ellipsoid. Ellipsoid heights are not the same as 
orthometric heights or elevations. Orthometric heights or elevations are 
obtained from conventional differential leveling. This distinction between 
ellipsoid heights and orthometric elevations is critical to many engineering 
and construction projects. GPS users must exercise extreme caution in 
applying GPS height determinations to projects that are based on orthometric 
elevations. 

8-64. The GPS uses WGS 84 as the optimal mathematical model best 
describing the shape of the true earth at sea level, based on an ellipsoid of 
revolution. The WGS-84 ellipsoid adheres very well to the shape of the earth 
in terms of horizontal coordinates but differs somewhat with the established 
MSL definition of orthometric height. The difference between ellipsoidal 
height (as derived by the GPS) and conventional leveled (orthometric) heights 
is required over an entire project area to adjust GPS heights to orthometric 
elevations. The NGS has developed geoid modeling software (for example, 
GEOID93, GEOID96, and GEOID99) to be used to convert ellipsoidal heights 
to approximate orthometric elevations. These converted elevation values 
should be used with extreme caution because they are easy to mess up. 

8-65. Static- or kinematic-GPS-S techniques can be used effectively on a 
regional basis for the densification of low-accuracy vertical control for 
topographic mapping. Existing BM data (orthometric heights) and 
corresponding GPS-derived ellipsoidal values for at least three stations in a 
small project area can be used in tandem in a minimally constrained 
adjustment program to reasonably model the geoid. More than three 
correlated stations are required for larger areas to ensure proper modeling 
from the BM data. Corresponding GPS data can then be used to derive the 
unknown orthometric heights of the remaining stations that were occupied 
during the G PS-observation period. 



NAVSTARGPS 8-17 



FM 3-34.331 



GEOID HEIGHTS 



8-66. The impact of the GPS on geodetic-control surveys has been immense. 
I n the past, surveyors relied on line-of-sight instrumentation to develop 
coordinates. With the GPS, ground-station intervisibility is no longer 
required, and much longer lines can be surveyed. Different instruments and 
survey methods were used to measure horizontal and vertical coordinates, 
leading to two different networks with little overlap. The GPS, on the other 
hand, is a 3D system. 

8-67. The heights obtained from the GPS are in a different height system 
than those historically obtained with geodetic leveling. GPS data can be 
readily processed to obtain ellipsoidal heights. This is the height above or 
below a simple ellipsoid model of the earth. Geodetic leveling takes into 
consideration a height called orthometric height (often known as the height 
above the MSL). These heights are found on topographic maps, stamped on 
markers, or stored in innumerable digital and paper data sets. To transform 
between these height systems requires thegeoid height. These height systems 
are related by the following equation: 

h=H +N 



where— 

h =d I ipsoidal height 
H = orthometric height 
N =geoid height 

DIFFERENTIAL ERROR SOURCES 



8-68. Error sources encountered when using DGPS techniques are the same 
as for absolute positioning. I n addition to these error sources, the receiver 
must maintain satellite lock on at least three satellites for 2D positioning and 
four satellites for 3D positioning. When loss of lock occurs, a cycle slip 
(discontinuity of an integer number of cycles in the measured carrier-beat 
phase as recorded by the receiver) may occur. I n GPS absolute surveying, if 
satellite lock is not maintained, positional results will not be formulated. In 
GPS static surveying, if satellite lock is not maintained, positional results 
may be degraded resulting in incorrect formulations. In GPS static surveying, 
if the observation period is long enough, postprocessing software may be able 
to average out loss of lock and cycle slips over the duration of the observation 
period and formulate adequate positional results. If this is not the case, 
reoccupation of the stations may be required. In all differential-surveying 
techniques, if loss of lock does occur on some of the satellites, data processing 
can continue easily if a minimum of four satellites have been tracked. 
Generally, the more satellites tracked by the receiver, the more insensitive 
the receiver is to loss of lock. Cycle slips can usually be compensated. 



DIFFERENTIAL ACCURACIES 



8-69. There are two levels of accuracy obtainable from the GPS when using 
differential techniques. The first level is based on pseudorange formulations, 
whilethe other is based on carrier-beat-phase formulations. 



8-18 NAVSTARGPS 



FM 3-34.331 



PSEUDORANGE FORMULATIONS 



8-70. Pseudorange formulations can be developed from either the C/A-code or 
the more precise P-code. Pseudorange accuracies are generally accepted to be 
1 percent of the period between successive code epochs. Use of the P-code, 
where successive epochs are 0.1 millisecond apart, produces results that are 
about 1 percent of 0.1 millisecond (about 1 nanosecond). Multiplying this 
value by the speed of light gives a theoretical-resultant range measurement of 
around 30 centimeters. If using pseudorange formulations with the C/A-code, 
results can be ten times less precise (a range-measurement precision of 
around 3 meters). Point-positioning accuracy for a differential pseudorange 
solution is generally found to be in the range of 0.5 to 10 meters. These 
accuracies are largely dependent on the type of GPS receiver being used. 



CARRIER-BEAT-PHASE FORMULATIONS 



8-71. Carrier-beat-phase formulations can be based on either the LI, the L2, 
or both carrier signals. Accuracies achievable using carrier-beat-phase 
measurement are generally accepted to be 1 percent of the wavelength. Using 
the LI frequency, where the wavelength is around 19 centimeters, a 
theoretical-resultant range measurement that is 1 percent of 19 centimeters 
(about 2 millimeters). The L2 carrier can only be used with receivers that 
employ a cross correlation, squaring, or another technique to get around the 
effects of AS. 

8-72. The final positional accuracy of a point, that was determined using 
DGPS survey techniques, is directly related to the geometric strength of the 
configuration of satellites observed during the survey session. GPS errors 
resulting from satellite-constellation geometry can be expressed in terms of 
DOP. Positional accuracy for a differential carrier-beat-phase solution is 
generally in a range of 1 to 10 millimeters. 

8-73. In addition to G DOP, PDOP, HDOP, and VDOP, the quality of the 
baselines produced by the DGPS (static or kinematic) through carrier-phase 
recovery can be defined by a quantity called relative DOP (RDOP). 
Multiplying the uncertainty of a double-difference measurement by RDOP 
yields the relative position error for that solution. The values of RDOP are 
measured in meters of error in relative position per error of one cycle in the 
phase measurement. The knowledge of an RDOP, or an equivalent value, is 
extremely important to the confidence one assigns to a baseline recovery. 
RDOP represents position recovery over a whole session of time and is not 
representative of a position recovery at an instant in time. When carrier- 
phase recovery is used, RDOP values around 0.1 meter per cycle are 
considered acceptable. 



SECTION IV - PRECISE-POSITIONING SURVEY PLANNING 



8-74. Using differential carrier-phase surveying to establish control for 
military projects requires operational and procedural specifications. These 
specifications area project-specific function of the control being established. 
To accomplish these surveys in the most efficient and cost-effective manner 
and toensure that the required accuracy is obtained, detailed survey planning 



NAVSTARGPS 8-19 



FM 3-34.331 



is essential. This section defines GPS-S design criteria and other 
specifications that are required to establish control for topographic-survey 
projects. 



PROJ ECT-CONTROL ACCURACY 



8-75. The first step in planning a control survey is to determine the ultimate 
accuracy requirements. Survey accuracy requirements area direct function of 
the project's functional needs, that is, the basic requirements needed to 
support the planning, engineering design, maintenance, and operation. This is 
true for GPS or conventional surveying to establish project control. Most 
military activities require relative accuracies (accuracies between adjacent 
control points) ranging from 1:1,000 to 1:50,000, depending on the nature and 
scope of the project. Few topographic projects demand positional accuracies 
higher than 1:50,000 (second-order, Class I ). 



FUNCTIONAL REQUIREMENTS 



8-76. Functional requirements must include planned and future design and 
mapping activities. Specific control density and accuracy are derived from 
these functional requirements. Control density within a given project is 
determined from factors such as planned construction, site-plan and master- 
plan mapping scales, and artillery/aviation-survey positioning requirements. 
The relative accuracy for project control is also determined based on such 
things as mapping scales, design needs, and project type. Most site-plan 
mapping for design purposes is performed and evaluated relative to the 
American Society of Photogrammetry and Remote Sensing (ASPRS) 
standards. These standards apply to photogrammetric mapping, plane-table 
mapping, and total-station mapping. Network control must be of sufficient 
relative accuracy to enable other users to reliably connect any supplemental 
mapping work. 



MINIMUM ACCURACY REQUIREMENTS 



8-77. Project control surveys should be planned, designed, and executed to 
achieve the minimum accuracy demanded by the functional requirements. To 
most efficiently use resources, control surveys should not be designed or 
performed to achieve accuracy levels that exceed the project requirements. 
For instance, if a third-order, Class I accuracy standard (1:10,000) is required 
for most topographic-project survey control, field-survey criteria should be 
designed to meet this minimum standard. 



ACHIEVABLE GPS ACCURACY 



8-78. GPS-S methods are capable of providing significantly higher relative 
positional accuracies with only minimal field observations, as compared with 
conventional triangulation or a traverse. Although a GPS-S may be designed 
and performed to support lower-accuracy project-control requirements, the 
actual results could be several magnitudes better than the requirement. 
Although higher accuracy levels are relatively easy to achieve with the GPS, it 
is important to consider the ultimate use of the control on the project when 
planning and designing GPS control networks. GPS-S adequacy evaluations 
should be based on the project's accuracy standards, not those theoretically 
obtainable with the GPS. 



8-20 NAVSTARGPS 



FM 3-34.331 



NETWORK-DESIGN FACTORS 

8-79. Many factors need to be considered when designing a GPS network and 
planning any subsequent observation procedures. These factors are described 
below. 

PROJ ECTSIZE AND REQUIRED DENSITY OF CONTROL 

8-80. The extent of the project will affect the GPS-S network shape. The type 
of GPS-S scheme used will depend on the number and spacing of points to be 
established as specified in the project requirements. In addition, maximum 
baseline lengths between stations and/or existing control are also prescribed. 
Often, a combination of GPS-S and conventional-survey densification is the 
most effective approach. 

ABSOLUTE GPS REFERENCE DATUMS 

8-81. Coordinate data for baseline observations are referenced and reduced 
relative to the WGS-84 ECEF coordinate system (X, Y, and Z). For all 
practical purposes, this system is not directly referenced to, but is closely 
related to, GRS 80 upon which NAD 83 is related (for CONUS work). Data 
reduction and adjustment are normally performed using the WGS-84 ECEF 
coordinate system, with baseline- vector components measured relative to the 
ECEF coordinate system. The baseline-vector components are denoted by 
delta [A] X, AY, andAZ. 

8-82. If the external network being connected and adjusted to is a part of or 
belongs to NAD 83, the baseline coordinates may bedirectly referenced on the 
GRS-80 ellipsoid since they are nearly equal. All supplemental control that is 
established is therefore referenced totheGRS-80/NAD-83 coordinate system. 

8-83. If a GPS-S is connected to NAD-27 stations that were not adjusted to 
NAD-83 datum, then these fixed points may be transformed to NAD-83 
coordinates using Corpscon, and the baseline reductions and adjustments are 
performed relative to the GRS-80 ellipsoid. This method is recommended only 
if resurveying is not a viable option. 

8-84. Alternatively, baseline connections to NAD-27 project control may be 
reduced and adjusted directly on that datum with resultant coordinates on the 
NAD 27. Geocentric coordinates on NAD-27 datum may be computed using 
transformation algorithms. Conversions of final adjusted points on NAD-27 
datum to NAD 83 may also be performed using Corpscon. 

8-85. Ellipsoid heights that are referenced to the GRS-80 ellipsoid differ 
significantly from the orthometric elevations. This difference (geoidal 
separation) can usually be ignored for horizontal control. Datum systems 
other than NAD 27/NAD 83 will be used outside CONUS (OCONUS) 
locations. Selected military operational requirements in CONUS may also 
require non-NAD datum references. It is recommended that GPS baselines be 
directly adjusted on the specific-project datum. 

CONNECTIONS TO EXISTING CONTROL 

8-86. For most static and kinematic GPS horizontal-control work, at least two 
existing control points should be connected for referencing and adjusting a 



NAVSTARGPS 8-21 



FM 3-34.331 



new GPS-S. Table8-5 shows GPS-S design, geometry, connection, and 
observing criteria. Existing points may be part of theNGRS or in-pl ace project 
control that has been adequately used for years. Additional points may be 
connected if practical. I n some instances, a single existing point may be used 
to generate spurred basel i ne vectors for supplemental construction control. 

Table 8-5. GPS-S Design, Geometry, Connection, and Criteria 



Criterion 


Classification Order 


2nd, 1 


2nd, II 


3rd, 1 


3rd, II 


Relative accuracy: 
ppm 
1 part in 


20 
50k 


50 
20k 


100 
10k 


200 
5k 


NGRS network (local project network) (W/F/P) 


Yes 


Yes 


Yes 


Yes 


Baseline observation check required over existing control 


Yes 


W/F/P 


W/F/P 


No 


Number of connections with existing network 
(NGRS or local project control): 

Minimum 

Optimum 


2 

3 


2 

3 


2 
2 


2 
2 


New point spacing not less than (m) 


1,000 


500 


200 


100 


Maximum distance from network to nearest control point 
in project (km) 


50 


50 


50 


50 


Minimum network control quadrant location 
(relative to project center) 


2 


N/R 


N/R 


N/R 


Master of fiducial stations required 


W/F/P 


No 


No 


No 


Loop closure criteria: 

Maximum number of baselines/loop 
Maximum loop length not to exceed (km) 
Loop misclosure not less than (ppm) 
Single spur baseline observations: 

Allowed per order/class 

Required number of sessions/baseline 

Required tie to NGRS 


10 
100 
20 

No 
NA 
NA 


20 
200 
50 

No 
NA 
NA 


20 

N/R 

100 

Yes 
2 
No 


20 

N/R 

200 

Yes 
2 
No 


Field-observing criteria (static GPS-Ss): 

Required antenna phase height measurement 
per session 

Meteorological observations required 

Two frequency L1/L2 observations required: 

< 50-km lines 

> 50-km lines 

Recommended minimum observation time 
(per session) (min) 

Minimum number of sessions per GPS baseline 

Satellite quadrants observed (minimum number) 

Minimum obstruction angle above horizon (deg) 


2 

No 

No 
Yes 

60 

1 

3 W/F/P 
15 


2 

No 

No 
Yes 

45 

1 
N/R 
15 


2 

No 

No 
Yes 

30 

1 
N/R 
15 


2 

No 

No 
Yes 

30 

1 
N/R 
15 



8-22 NAVSTARGPS 



FM 3-34.331 



Table 8-5. GPS-S Design, Geometry, Connection, and Criteria (continued) 



Criterion 


Classification Order 


2nd, I 


2nd, II 


3rd, 1 


3rd, II 


Maximum HDOP/VDOP during session 


N/R 


N/R 


N/R 


N/R 


Photograph and/or pencil rubbing required 


A/R 


No 


No 


No 


Kinematic GPS surveying: 

Allowable per survey class 

Required tie to NGRS 

Measurement time/baseline 

(follow manufacturer's specifications) 

Minimum number of reference points 

Preferred references 

Maximum PDOP 

Minimum number of observations from 
each reference station 


Yes 

W/F/P 

A/R 

2 
2 

15 

2 


Yes 

W/F/P 

A/R 

2 
2 

15 

2 


Yes 
No 

A/R 

1-2 
2 

15 

2 


Yes 

No 

A/R 

1 
1 
15 

2 


Adjustment and data submittal criteria: 
Approximate adjustments allowed 
Contract acceptance criteria: 

Type of adjustment 

Evaluation statistic 

Error-ellipse sizes 

Histogram 
Reject criteria: 

Statistic 

Standard 
Optimum/nominal weighting: 

Horizontal 

Vertical 
Optimum variance of unit weight 
GPS station/session data recording format 
Final station descriptions 
Written project/adjustment report required 


Yes 

Free (unconstrained) 

Relative distance accuracies 

(not used as criteria) 

(not used as criteria) 

Normalized residual 
±3 • SEUW 

±5 + 2 ppm 

±10 + 2 ppm 

Between 0.5 and 1 .5 

Field-survey book or form 

Standard DA form 

Yes 


LEGEND: 

W/F/P = where feasible and practical 

N/R = no requirement for this specification (usually indicates variance with provisional FGCC GPS 

specifications) 
A/R = as required in specific project instructions or manufacturer's operating manual 
SEUW = standard error of unit weight 



Connections With Existing Project Control 



8-87. The first choice for referencing new GPS-Ss is the existing project 
control. This is true for most surveying methods and has considerable legal 
basis. Unless a newly authorized project is involved, long-established project- 
control reference points should be used. If the project is currently on a local 
datum, then a supplemental tie to the NGRS should be considered as part of 
the project. 



NAVSTARGPS 8-23 



FM 3-34.331 



Connections With the NGRS 



8-88. Connections with the NGRS (for example, National Ocean Service/NGS 
control on NAD 83) are preferred where prudent and practical. As with 
conventional surveying, such connections to the NGRS are not mandatory. In 
many instances, connections with the NGRS are difficult and may add undue 
costtoa project with limited resources. When existing project control is known 
to be of poor accuracy, then ties (and total readjustment) to the NGRS may be 
warranted. Sufficient project funds should be programmed to cover the 
additional costs of these connections, including data submittal and review 
efforts if such work is intended to be included in the NGRS. 



Mixed NGRS and Project-Control Connections 



8-89. NGRS-referenced points should not be mixed with existing project 
control. This is especially important if existing project control was poorly 
connected with the older NGRS (NAD 27) or if the method of this original 
connection is uncertain. Since NGRS control has been readjusted to NAD 83 
(including subsequent high-precision HARNs readjustments of NAD 83) and 
most project control has not, problems may result if these schemes are mixed 
indiscriminately. If a decision is made to establish or update control on an 
existing project and connections with the NGRS (for example, NAD 83) are 
required, then all existing project-control points must be resurveyed and 
readjusted. Mixing different reference systems can result in different datums, 
causing adverse impacts on subsequent construction or boundary references. 
It is far more preferable to use "weak" existing project control for a reference 
rather than end up with a mixture of different systems or datums. 



Accuracy of Connected Reference Control 



8-90. Connections should be made to control stations with a higher order of 
accuracy than is required. This is usually the case where NGRS control is 
readily available. However, when only existing project control is available, 
connection and adjustment will have to be performed using that reference 
system, regardless of its accuracy. GPS-baseline measurements should be 
performed over existing control to assess its accuracy and adequacy for 
adjustments or to configure partially constrained adjustments. 



Connection Constraints 



8-91. Table8-5, pages 8-22 and 8-23, indicates that a minimum of two 
existing stations are necessary to connect GPS static and kinematic surveys 
reliably. It is often prudent to include additional NGRS and/or project points, 
especially if the existing network is not reliable. Adding additional points will 
provide redundant checks on the surrounding network. This allows for the 
elimination of these points if the final constrained adjustment indicates a 
problem with one or more of the fixed points. This table also indicates the 
maximum-allowable distance that GPS baselines should extend from the 
existing network. Federal Geodetic Control Subcommittee (FGCS) GPS 
standards (FGCC 1988) require connections to be spread over different 
quadrants relative to the survey project. Other GPS standards suggest an 
equilateral distribution of fixed control on the proposed survey area. 



8-24 NAVSTARGPS 



FM 3-34.331 



LOCATION FEASIBILITY AND FIELD RECON 



Project Sketch 



8-92. A good advance recon of all marks within the project area is crucial to 
an expedient and successful GPS-S. The site recon should be completed before 
the survey is started. Surveyors should prepare a site sketch and a brief 
description of how to reach the point, since the individual performing the site 
recon may not be the one that returns to occupy the known or unknown 
station. 



8-93. A project sketch should be developed before any site recon is performed. 
The sketch should be on a l:50,000-scale map or another suitable drawing. 
Drawing the sketch on a map will assist the planner in determining site 
selections and travel distances between stations. 



Station Descriptions and Recovery Notes 



8-94. Station descriptions for all new monuments will be developed as the 
monuments are established. The format for these descriptions is discussed in 
Chapter 3. Recovery notes should be written for existing NGRS network 
stations and project-control points. Estimated travel times to all stations 
should be included in the description. I nclude road-travel, walking, and GPS- 
receiver breakdown and setup time. These times can be estimated during the 
initial recon. A site sketch should also be made. DA Form 1959 can be used for 
description/recovery notes. 



Way-Point Navigation 



8-95. Way-point navigation (optional on some receivers) allows the user to 
enter the geodetic position (usually latitude and longitude) of points of 
interest along a particular route. The GPS antenna (fastened to a vehicle or 
range pole) and receiver can then provide the user with navigational 
information. This information may include the distance and bearing to the 
point of destination (stored in the receiver), the estimated time to the 
destination, and the speed and course of the user. This information can then 
be used to guide the user to the point of interest. Way-point navigation may 
also be helpful in the recovery of control stations that do not have 
descriptions. If a user has the capability of real-time code-phase positioning, 
the way-point-navigational accuracy can be in the range of 0.5 to 10 meters. 



Site-Obstruction/Visibility Sketches 



8-96. Record the azimuth and vertical angle of all obstructions during the site 
recon. The azimuths and vertical angles should be determined with a compass 
and an inclinometer, because obstructions such as trees and buildings cause 
the GPS signal being transmitted from the GPS satellite to be blocked. It is 
also important to know the type of obstruction to determine if multipath 
might be a problem. The obstruction data are needed to determine if the 
survey site is suitable for GPS surveying. Obstruction data should be plotted 
in a station-visibility diagram as shown in Figure8-1, page8-26. GPS 
surveying requires that all stations have an unobstructed view 15° above the 
horizon and satellites below 10° should not be observed. 



NAVSTARGPS 8-25 



FM 3-34.331 



©T&TOM WD8M&MUITV DIAGRAM 



STATION NAME QtU>fMr4o ^33 
AGENCY (CAST IN> C \ gTg 
OBSERVER K. ftVli-rK 
DATE H/\£ 7a3 

Observer's Height 
■T <C B ft., in. 



NORTH 

'HORIZON 




EAST 



i.Z^CCCx 



MAP SCALE 

MAP SHEET CTic»«»*<<<--cft. 



ELEV (NGVDZt 1 311,182- M 

UT (NAD^i) Vcj* Jo'as: 7^7?3 

LONG ( NAD 83 ) //4 • /? ' Z7."5& VOS 



SOUTH 



Indicate the horizontal and vertical limits of all objects obstucting veiw 
of the sky exceeding IS degrees above the horizon. 



UP- 


! AZIMUTH 


.Y.5RT ANCLE. 


! DESCRIPTION 


!! NO.! AZIMUTH! VERT ANGLE 


DESCRIPTION 


1 


\3HTco' 


/*• 30' 


1 2i«r j^**»*ft 


.'Ml ! 




? 


!3*ft*»e' 


lH«^o' 


. PE*t 3»r»0«.l 


!!12 ! 




JL 


! 13» ft ?' 


I* *££}.!, 


! £«&£ Sniucf 


!!13 I i 




4 


! 8\'oo' 


)1*oo' 


iH/e^t PP 


!M4 ! ! 




5 


! £>5*io' 


11 • oa' 


!s/Ft*.£ T>P 


!!15 ! ! 




6 


!Z03»00' 


t?** 6 ' 


:Et>«.t h*.pl4 


me : : 




7 


! z.i**3a' 


3^*.<?,?' 


!P*A* rt*«>Lt 


!M7 ! ! 




a 


•S3 *•<*>' 


itl'-o- 


!I?t>d.t MAP*! 


1MB! ! 




9 ! 


! :m9 : ! 




10 • 


! !!?n ! ! 





Indicate distance, direction, frequency and power of known RF sources. 
Indicate distance, horizontal and vertical limits of any object in the 
vicinity that n)»v cause radio signals to be reflected (multipath). 



5J.O g.86 To gio~ v»«-t» \z° F.ac TS^jcb. 

Paobaoly /Vo-r A 77/M4t~ gf_ <LA*a,j><. /4ui.n path ) 



Figure 8-1. Sample Station-Visibility Diagram 

Suitability for Kinematic Observations 

8-97. Obstruction-free projects may be suitable for kinematic- rather than 
static-GPS surveys. The use of kinematic observations increases productivity 



8-26 NAVSTARGPS 



FM 3-34.331 



5 to 10 times over static procedures, while still providing adequate accuracy 
levels. On many projects, a mixture of static- and kinematic-GPS observations 
may prove to be the most cost-effective. 

On-Site Physical Restrictions and Existing Control 

8-98. The degree of difficulty in occupying points due to on-site physical 
restrictions (such as travel times, site access, multipath effects, and satellite 
visibility) should be anticipated. The need for redundant observations must 
also be considered. Additional GPS baselines may need to be observed 
between existing NGRS control to verify accuracy and/or stability. 

Satellite-Visibility Limitations 

8-99. There are at least four or five satellites in view at all times for most of 
CON US. However, some areas may have less visibility when satellite 
maintenance is being performed or when there are unhealthy satellites. 
Satellite-visibility charts of the GPS-satellite constellation are important for 
optimizing network configuration and observation schedules. 



Station-lntervisibility Requirements 



8-100. Project specifications may dictate station-intervisibility requirements 
for azimuth reference. These requirements may constrain the minimum 
station spacing. 



MULTIPLE/REPEAT BASELINE CONNECTIONS 



8-101. Table8-5, pages 8-22 and 8-23, lists recommended criteria for baseline 
connections between stations, repeat baseline observations, and multiple 
station occupations so that extensive redundancy will result from the collected 
data. Many of these standards were developed bytheFGCS for performing 
high -precision geodetic-control surveys. 



LOOP REQUIREMENTS 



8-102. A loop (traverse) provides the mechanism for performing field-data 
validation as well as final-adjustment accuracy analysis. Since loops of GPS 
baselines are comparable to traditional E DM E/taped traverse routes, 
misclosures and adjustments can be handled similarly. Most GPS-S networks 
(static or kinematic) end up with one or more interconnecting loops that are 
either internal from a single fixed point or external through two or more fixed 
network points. Loops should be closed off at the spacing indicated in and 
meet the criteria specified in Table8-5, pages 8-22 and 8-23, based on the 
total loop length. 

8-103. GPS control surveys may be conducted by forming loops between two 
or more existing points, with adequate cross-connections where feasible. Such 
alignment techniques are usually most practical on site plans or navigational 
projects that require control to be established along a linear path. Loops 
should be formed every 10 to 20 baselines, preferably closing on existing 
control. Connections to existing control should be made as opportunities exist 
and/or as often as practical. 



NAVSTARGPS 8-27 



FM 3-34.331 



8-104. When establishing control over such areas as relatively large military 
installations, perform a series of redundant baselines to form interconnecting 
loops. When densifying second- and third-order control for site-plan design 
and construction, extensive cross-connecting-loop and network configurations 
(recommended by the FGCS for geodetic surveying) are not necessary. 

8-105. On all projects, consider the maximum use of combined static- and 
kinematic-GPS observations. Both may be configured to form pseudotraverse 
loops for subsequent field-data validation and final adjustment. 



NETWORK DESIGN AND LAYOUT 



8-106. A wide variety of survey configurations may be used to densify project 
control using GPS surveying. Unlike conventional triangulation and EDM 
traverse surveying, the shape or geometry of the G PS-network design is not as 
significant. The following guidelines for planning and designing proposed 
GPS-Ss are intended to support lower-order (second-order, Class I, or 1:50,000 
or less accuracy) military control surveys where relative accuracies at the 
centimeter level or better are required over a small project area. Newly 
established GPS control may or may not be incorporated into the NGRS. This 
depends on the adequacy of the connection to the existing NGRS network or 
whether the connection was tied only internally to existing project control. 

8-107. When developing a network design, it is important to obtain the most 
economical coverage within the prescribed project -accuracy requirements. The 
optimum network design, therefore, provides a minimum amount of baseline/ 
loop redundancy without an unnecessary amount of observation. Obtaining 
this optimum design (cost versus accuracy) is difficult and changes constantly 
due to evolving GPS technology and satellite coverage. 

8-108. Planning a GPS-S scheme is similar to planning for conventional 
triangulation or traversing. The type of survey design used is dependent on 
the GPS technique and the user's requirements. 



GPS NETWORKING 



8-109. A GPS network is proposed when established survey control is to be 
used in precise-network densification (1:50,000 to 1:100,000). For lower-order 
work, elaborate network schemes are unnecessary and less work-intensive 
GPS-S methods may be used. The surveyor should devise a survey network 
that is geometrically sound. The networking method is practical only with 
static-, pseudokinematic-, and kinematic-survey techniques. Figure 8-2 shows 
a step-by-step example of how to design a GPS-S network. 



GPS TRAVERSING 



8-110. GPS traversing should be used when the user has only two or three 
receivers and the required accuracies are 1:5,000 to 1:50,000. Traversing with 
GPS is similar to conventional methods. Open-end traverses are not 
recommended when 1:5,000 accuracies or greater are required. The GPS does 
not provide sufficient point-positioning accuracies, so surveyors must have a 
minimum of one fixed (or known) control point, although three are preferred. 



8-28 NAVSTARGPS 



FM 3-34.331 



Step 1 
Session 1 




Step 3 
Session 3 




Step 5 
Session 5 




Step 2 
Session 2 




Step 4 
Session 4 




Step 6 
Session 6 



Figure 8-2. GPS-Network Design 

8-111. A fixed control point is a station with known latitude, longitude, and 
height or easting, northing, and height. This point may or may not be part of 
the NGRS. If only one control point is used and the station does not have a 
known height, the user will be unable to position the unknown stations. 

8-112. When performing a loop traverse, surveyors should observe a check 
angle or check azimuth using conventional-survey techniques to determine if 
the known station has been disturbed. If azimuth targets are not visible and a 
check angle cannot be observed, a closed traverse involving one or more 
control points is recommended. Again, a check angle or check azimuth should 
be observed from the starting control station. If a check angle is not 
performed, the survey can still be completed. However, if the survey does not 



NAVSTARGPS 8-29 



FM 3-34.331 



meet specified closure requirements, the surveyor will be unable to assess 
what control point may be in error. If a check angle or check azimuth cannot 
be observed, a third control point should be tied into the traverse to aid in 
determining the cause of misclosure (Figure 8-3). 



Open traverse 



-o 



Loop traverse 




Closed traverse 




LEGEND: 

A = known control 
O = unknown control 



Check angles should be 
observed when performing an 
open, loop, or closed traverse. 



Figure 8-3. G PS-Traversing Schemes 



GPS SPUR SHOTS 



8-113. GPS spurs shots are acceptable when the user has only two receivers 
or only a few control points are to be established. Spur lines should be 
observed twice during two independent observation sessions. Once the first 
session is completed, the receivers at each station should be turned off and the 
tripod elevations changed. This procedure is similar to performing a forward 
and backward level line. It is important that the tripods be moved in elevation 
and replumbed over the control station between sessions. If this step is not 
implemented, the two baselines cannot be considered independent. Spur shots 
are most applicable to static-survey and relative-positioning (code-phase) 
techniques. 



8-30 NAVSTARGPS 



FM 3-34.331 



GPS-S TECHNIQUES 



8-114. After a GPS network has been designed and laid out, a GPS-S 
technique needs to be considered. The most efficient technique should be 
chosen tominimizetimeand cost, while meeting the accuracy requirements of 
a given survey project. Once a technique is chosen, the equipment 
requirements, observation schedules, sessions designations, and planning 
functions can be determined. 



GENERAL EQUIPMENT REQUIREMENTS 



Receivers 



Personnel 



Transportation 



8-115. The type of GPS instrumentation used on a project depends on the 
accuracy requirements, the GPS-S technique, the project size, and economics. 
Dual-frequency receivers are recommended for baselines that exceed 
50 kilometers. The length of the baseline may vary depending on the amount 
of solar activity during the observation period. Using a dual-frequency 
receiver permits the user to solve for possible ionospheric and tropospheric 
delays, which can occur as the signal travels from the satellite to the receiver 
antenna. 



8-116. A minimum of two receivers is required to perform a DGPS survey. 
The actual number used on a project will depend on the project size and the 
number of available instruments and operators. Using more than two 
receivers will often increase productivity and field-observation efficiency. 
Some kinematic applications require two reference receivers (set at known 
points) and at least one rover receiver. 



8-117. Personnel requirements are also project dependent. Most GPS 
equipment is compact and lightweight and only requires one person per 
station setup. However, when a station is not easily accessible or requires 
additional power for a data link, two individuals may be required. 



8-118. Normally, one vehicle is required for each GPS receiver used. Vehicles 
should be equipped to handlethe physical conditions that may be encountered 
during the field observations. In most cases, a two-wheel-drive vehicle is 
adequate. If adverse site conditions exist, a four-wheel-drive vehicle may be 
required. Adequate and reliable transportation is important when the 
observation schedule requires moving from one station to another between 
observation sessions. 



Auxiliary Equipment 



8-119. Adequate power should be available for all equipment (such as, 
receivers, PCs, and lights) that will be used during the observations. PCs, 
software, and data-storage devices (floppy disks and/or cassette tapes) should 
be available for on-site field-data reduction. Other equipment should include 
tripods, tribrachs, tape measures, flags, flashlights, tools, equipment cables, a 



NAVSTARGPS 8-31 



FM 3-34.331 



compass, and an inclinometer. A data link is also needed if real-time 
positioning is required. 



OBSERVATION SCHEDULES 



8-120. Planning a GPS-S requires a determination of when satellites will be 
visible for the given survey area. The first step in determining observation 
schedules is to plot the satellite visibility for the project area. Even when the 
GPS becomes fully operational, a full two-hour coverage of at least four 
satellites may not be available in all areas. 

8-121. Most GPS-equipment manufacturers have software packages that 
predict satellite rise and set times. A satellite plot should have the satellites' 
azimuths, elevations, rise and set times, and PDOPs for the desired survey 
area. Satellite-ephemeris data is generally required as input for prediction 
software. 

8-122. To obtain broadcast-ephemeris information, a GPS receiver collects 
data during a satellite window. The receiver antenna does not have to be 
located over a known point when collecting a broadcast ephemeris. The data is 
then downloaded into a satellite-prediction software. Besides inputting 
ephemeris data, the approximate latitude and longitude (usually scaled from 
a topographic map) and the time offset from UTC for the survey area are 
generally required. 

8-123. The best time to perform a successful GPS-S can be obtained by taking 
advantage of the best combination of the satellites' azimuths, elevations, and 
PDOPs as determined by the satellite-visibility plot for the desired survey 
area. The number of sessions and/or stations observed per day will depend on 
the satellite visibility, the travel time between stations, and the final accuracy 
required. A receiver is often required to occupy a station for more than one 
session per day. 

8-124. A satellite sky plot (Figure8-4) and a PDOP versus time plot 
(Figure8-5, page8-34) should be run before a site recon. The output files 
created by the satellite-prediction software are used in determining if a site is 
suitablefor GPS surveying. 

8-125. Station occupation during each session should be designed to minimize 
travel time and to maximize the overall efficiency of the survey. 
Determination of session times is based mainly on the satellite-visibility plan 
with the following factors taken into consideration: 

• The time required to permit safe travel between survey sites. 

• The time to set up and take down the equipment before and after the 
survey. 

• The time to perform the survey. 

• The possible loss of observation time due to unforeseeable problems or 
complications. 



8-32 NAVSTARGPS 



FM 3-34.331 



Point: Shamberger Cube Lat 37:15:0 N Lon 93:23:0 W Almanac: Current.eph 2/18/99 

Date: Thursday, February 18, 1999 Threshold elevation 15 (deg) Time zone 'Central Day USA' -5:00 
27 satellites considered: 1 2 3 4 5 6 7 8 9 10 13 14 15 16 17 18 19 21 22 23 24 25 26 27 29 30 31 




25 E 



10:00 



T 



T 



~T 



T 



T 



T~ 



T 



10:30 11:00 11:30 12:00 12:30 

Time (major tick marks = 30 minutes) (sampling 10 minutes) 



13:00 



Figure 8-4. Sample Satellite Sky Plot 

SESSION DESIGNATIONS AND PLANNING FUNCTIONS 

8-126. A GPS-S session is a single period of observation. Station/session 
designations are usually denoted by alphanumeric characters (for example, 0, 
1, 2, A, B, C) and are determined before survey commencement. 

8-127. If the party chief states that only eight numeric characters are 
permitted for station/session designations, the convention would be 12345678 . 
The eight numeric characters are identified as follows: 

• First character. This character denotes the type of monument. The 
following convention is recommended: 

1 = known horizontal-control monument. 

2 = known BM. 

3 = known 3D monument. 

4 = new horizontal-control monument. 

5 = new B M . 



NAVSTARGPS 8-33 



FM 3-34.331 



Number SVs and PDOP 

Point: Shamberger Cube Lat 37:1 5:0 N Lon 93:23:0 W Almanac: Current.eph 2/1 8/99 

Date: Thursday, February 18, 1999 Threshold elevation 15 (deg) Time zone 'Central Day USA' -5:00 
27 satellites considered: 1 2 3 4 5 6 7 8 9 10 13 14 15 16 17 18 19 21 22 23 24 25 26 27 29 30 31 

12 



CO 



Q. 
O 
Q 
Q. 



8 
4 


20 

16 
12 _ 





:!::::::: 


F : -+ 


r"~~";"~"::::i:::::: 




z^zzzzztT----------- 


^ H 


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10:00 10:30 11:00 11:30 12:00 12:30 

Time (major tick marks = 30 minutes) (sampling 10 minutes) 



13:00 



Figure 8-5. PDOP Versus Time Plot 

6 =new 3D monument. 

7 = unplanned occupation. 

8 = temporary 2D point. 

9 = temporary 3D point. 

• Second, third, and fourth characters. These characters denote the 
actual station number given to the station. 

• Fifth, sixth, and seventh characters. These characters denote the 
J ulian day of the year. 

• E ighth character. This character denotes the session number. 

8-128. An example of a station designation is: 

Character position = 12345678 
Station identifier = 40011821 



8-34 NAVSTARGPS 



FM 3-34.331 



• The numeral 4 in the first position indicates that the monument is 
new and only the horizontal position is being established. 

• The numerals 001 are the station number for the monument. 

• The numerals 182 arethej ulian date. 

• The numeral 1 in the eighth position identifies the session number 
during which observations are being made. If the receiver performed 
observations during the second session on the same day on the same 
monument, the session number should be changed to 2 for the period 
of the second session. 

8-129. When alpha characters are permitted for a station/session designation, 
a more meaningful designation can be assigned. The date of each survey 
session should be recorded during the survey as calendar dates and J ulian 
days and used in the station/session designation. Some GPS software 
programs will requirej ulian dates. 

8-130. In addition to determining station/session designations, the following 
processes should be done before the survey begins: 

• Determine the occupant of each station. 

• Determine the satellite visibility for each station. 

• Request site-recon data for each station to be occupied (prior data may 
require clarification before survey commencement). 

Develop a project sketch. 

• Issue explicit instructions on when each session is to begin and end. 

• Complete a station data-logging sheet for each station. 



SECTION V - PRECISE-POSITIONING SURVEY CONDUCT 



8-131. This section presents guidance on field GPS-Ss for all types of projects. 
The primary emphasis in this section is on static and kinematic carrier-phase 
DGPS measurements. 

BASIC GPS-S PROCEDURES 

8-132. The following are some general DGPS field-survey procedures. They 
should be performed at each station or during each session on a GPS-S. 



RECEIVER SETUP 



8-133. GPS receivers shall be set up according to manufacturers' 
specifications before beginning any observations. To eliminate any possibility 
of missing the beginning of the observation session, all equipment should be 
set up and power should be supplied to the receivers at least 10 minutes 
before the beginning of the observation session. Most receivers will lock on to 
satellites within 1 to 2 minutes of power-up. 



ANTENNA SETUP 



8-134. All tribrachs should be calibrated and adjusted before beginning each 
project. Since centering errors represent a major error source in all survey 
work, use both optical plummets and standard plumb bobs. 



NAVSTARGPS 8-35 



FM 3-34.331 



HI MEASUREMENTS 



8-135. HI refers to the correct measurement of the distance of the GPS 
antenna above the reference monument over which it has been placed. Make 
HI measurements before and after each observation session, from the 
monument to a standard reference point on the antenna. Establish standard 
reference points for each antenna before the beginning of the observations. 
Make observations in both meters and feet for redundancy and blunder 
detection. Determine HI measurements to the nearest millimeter and to the 
nearest 0.01 foot. Note whether the HI is vertical or diagonal. 



FIELD OBSERVATION PROCEDURES 



8-136. Field-recording books, log sheets, log forms, or any acceptable 
recording media will be completed for each station and/or session. These 
records will be used for archival purposes. The amount of recording detail will 
depend on the project. Low-order geographic-mapping points do not need as 
much descriptive information as permanently marked primary-control points. 
U nit commands may require that additional data be recorded. These 
requirements are contained in the project instructions. The following data 
should be included in the field records: 

• Project name, project-directive number, observer name(s), and unit 
name. 

Station-designation number. 
Station file number. 
Date and weather conditions. 
Session start and stop time (local and UTC). 

Receiver, antenna, DRU, and tribrach make, model, and serial 
number. 

Antenna height (vertical or diagonal measures in inches [or feet] and 
centimeters [or meters]). 
Satellite-vehicle (SV) designation and number. 
Station-location sketch. 
Geodetic location and elevation (approximate). 
Problems encountered. 



FIELD PROCESSING AND VERIFICATION 



8-137. It is strongly recommended that GPS-data processing and verification 
be performed in the field (if applicable). This identifies any problems that may 
exist and can be corrected before returning from the field. 



ABSOLUTE POSITIONING 



8-138. The accuracy obtained by GPS point positioning is dependent on the 
user's authorization. The SPS user can obtain an accuracy of 80 to 100 meters. 
SPS data are most often expressed in real time; however, the data can be 
postprocessed if the station occupation was over a period of time. The 
postprocessing produces a best-fit point position. Although this will provide a 
better internal approximation, the effects of S/A still degrade a positional 
accuracy of 80 to 100 meters. PPS users require a decryption device within the 
receiver to decode the effects of S/A. PPS provides an accuracy between 10 and 



8-36 NAVSTARGPS 



FM 3-34.331 



16 meters when a single-frequency receiver is used for observation. Dual- 
frequency receivers using the precise ephemeris may produce an absolute- 
positional accuracy of 1 meter or better. These positions are based on the 
absolute WGS-84 ellipsoid. PPS uses precise ephemeris, which requires the 
data to be post processed. The military uses a GPS-S receiver that is capable of 
meter-level GPS point positioning without postprocessing. 

8-139. There are two techniques used for point positioning in the absolute 
mode— long-term averaging of positions and differencing between signals. In 
long-term averaging, a receiver is set up to observe and store positions over a 
period of time. The length of the observation time depends on the accuracy 
required. The longer the period of data collection, the more accurate the 
position. The observation times can range between 1 and 2 hours. This 
technique can also be used in real time (the receiver averages the positions as 
they are calculated). The process of differencing between signals can only be 
performed in a postprocessed mode. NIMA has produced software that can 
perform this operation. 



DIFFERENTIAL POSITIONING 



8-140. DGPS surveying is used to determine one location with respect to 
another location. When using this technique with the C/A- or P-code, it is 
called differential code-phase positioning or surveying. Differential code- 
phase positioning has limited application to detailed engineering surveying 
and topographic site-plan mapping applications. Exceptions include general 
recon surveys and military operational or geodetic-survey support functions. 
Additional applications for differential code-phase positioning have been on 
the increase as positional accuracy has increased. The code-phase-tracking 
differential system is a functional GPS-S system for positioning hydrographic- 
survey vessels and dredges. It also has application for small-scale, topographic 
mapping surveys or as input to a geographic-information-system (GIS) 
database. The collected data is used as input for a GIS database. A real-time 
dynamic DGPS positioning system includes a reference station, a 
communication link, and remote user equipment. If real-time results are not 
required, the communication link can be eliminated and the positional 
information postprocessed. Differential code-phase surveys can obtain 
accuracies of 0.5 to 0.05 meter. 



REFERENCE STATION 



8-141. A reference station is placed on a known survey monument in an area 
having an unobstructed view of at least four satellites that are 10° above the 
horizon. The reference station consists of a GPS receiver and antenna, a 
processor, and a communication link (if real-time results are desired). The 
reference station measures the timing and ranging information that is 
broadcast by the satellites and computes and formats range corrections for 
broadcast to the user's equipment. Using differential pseudoranging, the 
position of a survey vessel is found relative to the reference station. The 
pseudoranges are collected by the GPS receiver and transferred to the 
processor where PRCs are computed and formatted for data transmission. 
M any manufacturers have incorporated the processor within the GPS 
receiver, eliminating the need for an external processing device. The 
recommended data format is established by the Radio Technical Commission 



NAVSTARGPS 8-37 



FM 3-34.331 



for Maritime (RTCM) Services Special Committee (SC). The processor should 
be capable of computing and formatting PRCs every 1 to 3 seconds. 



COMMUNICATION LINK 



8-142. A communication link is used as a transfer media for differential 
corrections. The main requirement of the communication link is that 
transmission be at a minimum rate of 300 bits per second. The type of 
communication system is dependent on the user's requirements. 

Frequency Authorization 

8-143. All communication links necessitate a reserved frequency for operation 
to avoid interference with other activities in the area. No transmission can 
occur over a frequency until the frequency has been officially authorized for 
transmitting digital data. This applies to all government agencies. Allocating 
a frequency is handled by the responsible frequency manager. 

Ultrahigh-Frequency and Very-High-Frequency Broadcast Distance 

8-144. Communication links operating at ultrahigh frequency (UHF) and 
very-high frequency (VHF) are viable systems for the broadcast of DGPS 
corrections. UHF and VHF can extend out 20 to 50 kilometers, depending on 
local conditions. The disadvantages of UHF and VHF links are their limited 
range to line of sight and the effects of signal shadowing (for example, islands, 
structures, and buildings), multipath, and licensing issues. 

License-Free Radio Modems 

8-145. Several companies have developed low-wattage (1 watt or less) radio 
modems to transmit digital data. These radio modems require no license and 
can be used to transmit DGPS corrections in a localized area. The 
disadvantages of these radio modems is their limited range and line of sight. 

USER'S (RE MOTE -STATION) EQUIPMENT 

8-146. The remote receiver should be a multichannel dual-frequency Y-code 
GPS receiver. The receiver must be able to store raw data for postprocessing. 
During postprocessing, the PRCs are generated with the GPS data from the 
reference station and then applied to the remote-station data to obtain a 
correct position. If the results are desired in real time, the receiver must be 
able to accept the PRCs from the reference station (via a data link) in the 
RTCM Services SC format and apply those corrections to the measured 
pseudorange. The corrected position data can then be input and stored in a 
database. 

USCG DGPS NAVIGATION SERVICE 

8-147. The USCG DGPS Navigation Service was developed to provide a 
nationwide (coastal regions, Great Lakes regions, and some inland 
waterways), all-weather, real-time, radio-navigation service in support of 
commercial and recreational maritime interests. Its accuracy was originally 
designed to fulfill an 8- to 20-meter maritime-navigation accuracy. However, a 
reconfigured version of the USCG system now yields a 1.5-meter 2-deviation 
RMS at distances upward of 150 kilometers from the reference beacon. The 



8-38 NAVSTARGPS 



FM 3-34.331 



system operates on the USCG marine radio-beacon frequencies (285 to 
325 kilohertz). E ach radio beacon has an effective range of 150to 
250 kilometers at a 99.9 percent signal-availability level. It is fully expected 
that the U SCG system, once completed, will be the primary marine- 
navigation device used by commercial and recreational vessels requiring 
meter-level accuracy. 

DGPS CARRIER-PHASE HORIZONTAL-POSITIONING SURVEYS 

8-148. DGPS carrier-phase surveying is used to obtain the highest precision 
from the GPS and has direct application to most military topographic and 
engineering surveys. The following six, basic DGPS surveying techniques are 
in use: 

Static. 

Stop-and-go kinematic. 

Kinematic. 

Pseudokinematic. 

Rapid static. 

OTF/RTK. 

DGPS SURVEY TECHNIQUES 

8-149. Procedures for performing each of these techniques are described 
below and should be used as guidelines for conducting a field survey. Specific 
manufacturers' procedures should also be followed. Project horizontal-control 
densification can be performed using any one of these techniques. 
Procedurally, all six techniques are similar in that each measures a 3D 
basel i ne vector between a receiver at one point (usually of known local-project 
coordinates) and a second receiver at another point, resulting in a vector 
difference between the two occupied points. The major distinction between 
static and kinematic baseline measurements is the way the carrier-wave 
integer-cycle ambiguities are resolved; otherwise, they are functionally the 
same process. 

AMBIGUITY RESOLUTION 

8-150. Cycle ambiguity (or integer ambiguity) is the unknown number of 
whole carrier wavelengths between the satellite and the receiver. Successful 
ambiguity resolution is required for successful baseline formulations. 
Generally, static surveying can provide instrumental error and ambiguity 
resolution through long-term averaging and simple geometrical principles, 
resulting in solutions to a linear equation that produces a resultant position. 
Ambiguity resolution can also be achieved through a combination of 
pseudorange and carrier-beat measurements, which are made possible by the 
PRN modulation code. 

POSTOBSERVATION DATA REDUCTION 

8-151. All carrier-phase relative-surveying techniques (except OTF/RTK), 
requ i re postprocessi ng of the observed data to determi ne t he rel ati ve basel i ne- 
vector differences. OTF/RTK can be performed in a real-time or postprocessed 
mode. Postprocessing of observed satellite data involves the differencing of 
signal-phase measurements recorded by the receiver. The differencing process 



NAVSTARGPS 8-39 



FM 3-34.331 



reduces biases in the receiver and satellite oscillators and is performed with a 
PC. All baseline reductions should be performed in the field (if possible) to 
allow an on-site assessment of the survey adequacy. 



STATIC SURVEYING 



8-152. Static surveying is perhaps the most common technique of densifying 
project network control. Two GPS receivers are used to measure a GPS- 
baseline distance. The line between a pair of GPS receivers from which 
simultaneous GPS data have been collected and processed is a vector referred 
to as a baseline. The station coordinate differences are calculated in terms of a 
3D ECEF coordinate system that uses X, Y, and Z values based on the WGS-84 
ellipsoid. These coordinate differences are then subsequently shifted to the 
project's coordinate system. GPS receiver pairs are set up over stations of 
either known or unknown locations. Typically, one of the receivers is 
positioned over a point whose coordinates are known (or have been carried 
forward as on a traverse) and the second is positioned over another point 
whose coordinates areunknown, but desired. Both GPS receivers must receive 
signals from the same four (or more) satellites for a period of time that can 
range from a few minutes to several hours, depending on the conditions of 
observation and the precision required. 



STATIC BASELINE-OCCUPATION TIME 



8-153. Station-occupation time is dependent on the baseline length, the 
number of satellites observed, and theGPS equipment. I n general, 30 minutes 
to 2 hours is a good occupation time for baselines of 1 to 30 kilometers. A 
rough guideline for estimating station-occupation time is shown in Figure8-6. 

8-154. There is no definitive guidance for determining the baseline- 
occupation time; the results from the baseline reduction (and subsequent 
adjustments) will govern the adequacy of the observation irrespective of the 
actual observation time. The most prudent policy is to exceed the minimum 
estimated times, especially for lines where reoccupation would be difficult or 
field-data assessment capabilities are limited. 

8-155. For baselines longer than 50 kilometers, the ionosphere may have an 
adverse effect on the solution. When using a dual-frequency GPS receiver, 
adverse ionosphere effects can shorten the baseline length. 



SATELLITE-VISIBILITY REQUIREMENTS 



8-156. The selected stations must have an unobstructed view of the sky for at 
least 15° or greater above the horizon during the observation window. An 
observation window is the period of time when observable satellites are in the 
sky and the survey can be successfully conducted. 



COMMON SATELLITE OBSERVATIONS 



8-157. It is critical for a static-survey baseline reduction/solution that the 
receivers simultaneously observe the same satellites during the same time 
interval. For instance, if receiver number 1 observes a satellite constellation 
during the time interval 1000 to 1200 and receiver number 2 observes that 
same satellite constellation during the time interval 1100 to 1300, only the 



8-40 NAVSTARGPS 



FM 3-34.331 





180 








3 satellites 


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w 

E 


135 
90 


120 






4 satellites 
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10 


100 






Length of baseline (km) 





Figure 8-6. Station-Occupation Time 

period of common observation (1100 to 1200) can be processed to formulate a 
correct vector difference between these receivers. 



DATA POSTPROCESSING 



8-158. After completing the observation session, the received GPS signals 
from both receivers are processed in a PC to calculate the 3D baseline-vector 
components between the two observed points. From these vector distances, 
local or geodetic coordinates may be computed and/or adjusted. 



SURVEY CONFIGURATION 



8-159. Static baselines may be extended from existing control using a control- 
densification method. These methods include networking, traverse, spur 
techniques, or combinations thereof. Specific requirements are normally 
contained in the project's instructions. 



RECEIVER OPERATION AND DATA REDUCTION 



ACCURACY 



8-160. Receiver operation and baseline-data postprocessing requirements are 
manufacturer-specific. The user should consult and study the manufacturer's 
operations manual (including the baseline data-reduction examples). 



8-161. Accuracy of static surveys will usually exceed 1 ppm. Static is the most 
accurate of all GPS techniques and can be used for any order survey. 



NAVSTARGPS 8-41 



FM 3-34.331 



STOP-AND-GO KINEMATIC SURVEYING 



PROCEDURES 



8-162. Stop-and-go kinematic surveying is similar to static surveying in that 
it requires at least two receivers simultaneously recording observations. A 
major difference between static and stop-and-go surveying is the amount of 
time required for a receiver to stay fixed over an unknown point. I n stop-and- 
go surveying, the first receiver (the home or reference receiver) remains fixed 
on a known control point. The second receiver (the rover receiver) collects 
observations statically on a point of unknown position for a period of time 
(usually a few minutes) and then moves to subsequent unknown points to 
collect signals for a short period of time. During the survey, at least four 
(preferably five) common satellites need to be continuously tracked by both 
receivers. Once all required points have been occupied by the rover receiver, 
the observations are postprocessed by a PC to calculate the baseline-vector 
and coordinate differences between the known control point and points 
occupied by the rover receiver during the survey session. The main advantage 
of this technique over static surveying is the reduced occupation time required 
over the unknown points. Because less occupation time is required, the time 
spent and the cost of conducting the survey are significantly reduced. 
Achievable accuracies typically equal or exceed third order. 



8-163. Stop-and-go surveying is performed similarly to a conventional EDM 
traverse or electronic total-station radial survey. The GPS is initially 
calibrated by performing either an antenna swap (described below) with one 
known point and one unknown point or by performing a static measurement 
over a known baseline. This calibration process is performed to resolve initial 
cycle ambiguities. The known baseline may be part of the existing network or 
can be established using static-survey techniques. The roving receiver 
traverses between unknown points as if performing a radial-topographic 
survey. Typically, the points are double-connected, or double-run, as in a level 
line. Optionally, two fixed receivers may be used to provide redundancy on the 
remote points. With only 1 1/2 minutes at a point, production of coordinate 
differences is high and limited only by satellite observation windows, travel 
time between points, and overhead obstructions. 



SATELLITE LOCK 



8-164. During a stop-and-go survey, the rover station must maintain satellite 
lock on at least four satellites during the period of observation (the reference 
station must be observing at least the same four satellites). Loss of lock occurs 
when the receiver is unable to continuously record satellite signals or a 
transmitted satellite signal is disrupted and the receiver is not able to record 
it. If satellite lock is lost, the roving receiver must reobservethe last control 
station that was surveyed before loss of lock. The receiver operator must 
monitor the GPS receiver when performing a stop-and-go survey to ensure 
that loss of lock does not occur. Some manufacturers have incorporated an 
alarm into their receiver that warns the user when loss of lock occurs. 



8-42 NAVSTARGPS 



FM 3-34.331 



SITE CONSTRAINTS 



8-165. Survey-site selection and the route between rover stations to be 
observed are critical. All sites must have a clear view (a vertical angle of 15° or 
greater) of the satellites. The route between rover stations must be clear of 
obstructions so that the satellite signal is not interrupted. Each unknown 
station to be occupied should be occupied for a minimum of 1 1/2 minutes. 
Stations should be occupied two or three times to provide redundancy between 
observations. 



ANTENNA-SWAP CALIBRATION 



ACCURACY 



8-166. Although antenna-swap calibration can be used to initialize a stop- 
and-go survey, it can also be used to determine a precise baseline and azimuth 
between two points. Both stations occupied and the path between both 
stations must maintain an unobstructed view of the horizon. A minimum of 
four satellites and maintainable satellite lock are required; however, more 
than four satellites are preferred. One receiver/antenna is placed over a 
known control point and the second receiver/antenna is placed a distance of 
10 to 100 meters away from the first receiver. The receivers at each station 
collect data for about 2 to 4 minutes. Then the receiver/antenna locations are 
swapped. The receiver/antenna at the known station is moved to the unknown 
site while the other receiver/antenna is moved to the known site. Satellite 
data are again collected for 2 to 4 minutes. The receivers are then swapped 
back to their original locations. This completes one antenna-swap calibration. 
If satellite lock is lost, the procedure must be repeated. 



8-167. Accuracy of stop-and-go baseline measurements will usually exceed 
1 part in 5,000; thus, third-order classification for horizontal control can be 
effectively, efficiently, and accurately established using this technique. For 
many projects, this order of horizontal accuracy will be more than adequate; 
however, field procedures should be designed to provide adequate redundancy 
for open-ended or spur points. Good satellite geometry and minimum 
multipath are also essential for performing acceptable stop-and-go surveys. 



KINEMATIC SURVEYING 



8-168. Kinematic surveying using differential carrier-phase tracking is 
similar to stop-and-go and static surveying because it also requires two 
receivers to record observations simultaneously. Kinematic surveying is often 
referred to as dynamic surveying. As in stop-and-go surveying, the reference 
receiver remains fixed on a known control point while the roving receiver 
collects data on a constantly moving platform (for example, a vehicle, a vessel, 
an aircraft, or a backpack). Kinematic surveying techniques do not require the 
rover receiver to remain motionless over the unknown point. The observed 
data is postprocessed with a PC, and the relative vector/coordinate differences 
to the roving receiver are calculated. 



NAVSTARGPS 8-43 



FM 3-34.331 



PROCEDURES 



8-169. A kinematic survey requires two single-frequency (LI) receivers. One 
receiver is set over a known point (reference station) and the other is used as a 
rover. Before the rover receiver can move, a period of static initialization or an 
antenna swap must be performed. This period of static initialization is 
dependent on the number of satellites visible. Once this is done, the rover 
receiver can move from point to point as long as satellite lock is maintained on 
at least four common satellites (common with the known reference station). If 
loss of lock occurs, a new period of static initialization must take place. It is 
important to follow the manufacturers' specifications when performing a 
kinematic survey. 



DATA PROCESSING 



ACCURACY 



8-170. Kinematic data-processing techniques are similar to those used in 
static surveying. When processing kinematic GPS data, the user must ensure 
that satellite lock was maintained on four or more satellites and that cycle 
slips were adequately resolved within the data recorded. 



8-171. Kinematic-survey errors are correlated between observations received 
at the reference and rover receivers. Test results indicate kinematic surveys 
can produce results in centimeters. Test results from a full-kinematic GPS-S 
conducted by TEC personnel at White Sands Missile Range verified (under 
ideal test conditions) that kinematic GPS surveying could achieve centimeter- 
level accuracy for distances of up to 30 kilometers. 



PSEUDOKINEMATIC SURVEYING 



PROCEDURES 



8-172. Pseudokinematic surveying is similar to kinematic surveying except 
that loss of lock is tolerated when the receiver is transported between 
occupation sites (the roving receiver can be turned off during movement, but 
this is not recommended). This feature provides the surveyor with a more 
favorable positioning technique since obstructions such as a bridge overpass, 
tall buildings, and overhanging vegetation are common. Loss of lock that may 
result due to these obstructions is more tolerable when pseudokinematic 
techniques are employed. M ission planning is essential for conducting a 
successful pseudokinematic survey. Especially critical is the determination of 
whether or not common satellite coverage will be present for the desired 
period of the survey. 



8-173. Pseudokinematic surveying requires that one receiver must 
continuously occupy a known control station. A rover receiver occupies each 
unknown station for 5 minutes. About 1 hour after the initial station 
occupation, the same rover receiver must reoccupy each unknown station. 



COMMON SATELLITE REQUIREMENTS 



8-174. Pseudokinematic surveying requires that at least four of the same 
satellites be observed between the initial station occupations and the requisite 



8-44 NAVSTARGPS 



FM 3-34.331 



reoccupation. For example, the rover receiver occupies Station A for the first 
5 minutes and tracks satellites 6, 9, 11, 12, and 13; then 1 hour later, during 
the second occupation of Station A, the rover receiver tracks satellites 2, 6, 8, 
9, and 19. Only satellites 6 and 9 are common to the two sets, so the data 
cannot be processed because four common satellites were not observed 
between the initial station occupation and the requisite reoccupation. 



DATA PROCESSING AND ACCURACY 



8-175. Pseudokinematic-survey satellite-data records and resultant baseline 
processing are similar to those performed for static GPS-Ss. Since 
pseudokinematic surveying requires each station to be occupied for 5 minutes 
and then reoccu pied for 5 minutes about one hour later, it is not suitable when 
control stations are widely spaced and transportation between stations within 
the allotted time is impractical. Pseudokinematic-surveying achieves 
accuracies of a few centimeters. 



RAPID-STATIC SURVEYING 



PROCEDURES 



8-176. Rapid-static surveying is a combination of stop-and-go kinematic, 
pseudokinematic, and static surveying. The rover receiver spends only a short 
time on each station (loss of lock is allowed between stations) and accuracies 
are similar to static surveying. However, rapid-static surveying does not 
require reobservation of remote stations like pseudokinematic surveying. 
Rapid-static surveying requires the use of dual-frequency GPS receivers with 
either cross correlation or squaring or any other technique used to compensate 
for AS. 



8-177. Rapid-static surveying requires that one receiver be placed over a 
known control point. A rover receiver occupies each unknown station for 5 to 
20 minutes, depending on the number of satellites and their geometry. 
Because most receiver operations are manufacturer-specific, following the 
manufacturers' guidelines are important. 



DATA PROCESSING AND ACCURACY 



8-178. Data should be processed according to the manufacturers' 
specifications. Accuracies are similar to static surveys of 1 centimeter or less. 
Rapid-static surveying can be used for medium- to high-accuracy surveys up 
to 1:1,000,000. 



OTF/RTK SURVEYING 



8-179. OTF/RTK surveying is similar to kinematic surveying because it 
requires two receivers that record observations simultaneously and allows the 
rover receiver to be moving. Unlike kinematic surveying, OTF/RTK surveying 
uses dual-frequency GPS observations and can handle loss of lock. OTF/RTK 
surveying uses the L2 frequency, and the GPS receiver must be capable of 
tracking the L2 frequency during AS. Two techniques that are used to obtain 
L2 during AS include squaring and cross correlation. 



NAVSTARGPS 8-45 



FM 3-34.331 



AMBIGUITY RESOLUTION 



PROCEDURES 



8-180. Successful ambiguity resolution is required for successful baseline 
formulations. The OTF/RTK technology allows the rover receiver to initialize 
and resolve baseline integers without a period of static initialization. If loss of 
lock occurs, reinitialization can be achieved whilethe remote is in motion. The 
integers can be resolved at the rover receiver within 10 to 30 seconds, 
depending on the distance from the reference station. OTF/RTK surveying 
requires that the L2 frequency be used in the ambiguity resolution. After the 
integers are resolved, only the LI C/A-codeis used to compute the positions. 



8-181. OTF/RTK surveying requires dual-frequency GPS receivers. One of the 
GPS receivers is set over a known point and theother is placed on a moving or 
mobile platform. If the survey is performed in real time, a data link and a 
processor (external or internal) are needed. The data link is used to transfer 
the raw data from the reference station to the remote. If the OTF/RTK 
surveying is performed with an internal processor, follow the manufacturers' 
guidelines. If OTF/RTK surveying is performed with external processors, the 
PC at the reference station collects and formats the raw GPS data and sends it 
via a data link to the rover receiver. A notebook computer at the rover receiver 
is used to process the raw data from the reference and remote receivers to 
resolve the integers and obtain a position. 



8-182. OTF/RTK surveys are accurate to within 10 centimeters when the 
distance from the reference receiver to the rover receiver does not exceed 
20 kilometers. The results of testing by the TEC produced accuracies of less 
than 10 centimeters. 



SECTION VI - PRECISE-POSITIONING SURVEY-DATA PROCESSING 



8-183. GPS-baseline solutions are usually generated through an iterative 
process. Using approximate values of the positions occupied and observation 
data, theoretical values for the observation period are developed. Observed 
values are compared to computed values and an improved set of positions 
occupied is obtained using least-squares-minimization procedures and 
equations that model potential error sources. This section discusses general 
postprocessing issues. Due to the increasing number and variety of software 
packages available, consult the manufacturer's guidelines when appropriate. 
Processing time is dependent on the accuracy required, the software, the PC, 
the data quality, and the amount of data. In general, high-accuracy solutions, 
crude computer software and hardware, low-quality data, and high volumes of 
data require longer processing times. Special care must be taken when 
attempting a baseline formulation with observations from different brands of 
GPS receivers. It is important to ensure that observables being used for the 
formulation of the baseline are of common format. 



ACCURACY 



PROCESSING TECHNIQUES 



8-184. The capability to determine positions using the GPS is dependent on 
the abi I ity to determi ne the range or distance of the satel I ite from the recei ver 



8-46 NAVSTARGPS 



FM 3-34.331 



located on the earth. There are two general techniques used to determine this 
range— pseudoranging and carrier-beat-phase measurement. 



PSEUDORANGING 



8-185. The observable pseudorange is calculated from observations recorded 
during a GPS-S. The observable pseudorange is the difference between the 
time of signal transmission from the satellite (measured in the satellite time 
scale) and the time of signal arrival at the receiver antenna (measured in the 
receiver time scale). When the differences between the satellite and the 
receiver clocks are reconciled and applied to the pseudorange observations, 
the resulting values are corrected pseudorange values. The value found by 
multiplying this time difference by the speed of light is an approximation of 
the true range between the satellite and the receiver. The value can be 
determined if ionosphere and troposphere delays, ephemeris errors, 
measurement noise, and unmodeled influences are taken into account when 
pseudoranging calculations are performed. A pseudorange can be obtained 
from either the C/A-code or the more precise P-code. 

CARRIER-BEAT-PHASE OBSERVATIONS 

8-186. The observable carrier-beat phase is the phase of the signal remaining 
after the internal oscillated frequency that is generated in the receiver is 
differenced from an incoming carrier signal of the satellite. The observable 
carrier-beat phase can be calculated from the incoming signal or from 
observations recorded during a GPS-S. By differencing the signal over a 
period or epoch of time, the number of wavelengths that cycle through the 
receiver during any given specific duration of time, can be counted. The 
unknown cycle count passing through the receiver over a specific duration of 
time is known as the cycle ambiguity. There is one cycle-ambiguity value per 
satellite/receiver pair as long as the receiver maintains continuous phase lock 
during the observation period. The value found by measuring the number of 
cycles going through a receiver during a specific time, when given the 
definition of the transmitted signal in terms of cycles per second, can be used 
to develop a time measurement for transmission of the signal. The time of 
transmission of the signal can be multiplied by the speed of light to yield an 
approximation of the range between the satellite and the receiver. The biases 
for carrier-beat-phase measurements are the same as for pseudoranges, 
although a higher accuracy can be obtained using the carrier. A more exact 
range between the satellite and the receiver can be formulated when the 
biases are taken into account during derivation of the approximate range 
between the satellite and the receiver. 

BASELINE SOLUTION BY LINEAR COMBINATION 

8-187. The accuracy achievable by pseudoranging and carrier-beat-phase 
measurement in both absolute- and relative-positioning surveys can be 
improved through processing that incorporates differencing of the 
mathematical models of the observables. Processing by differencing takes 
advantage of the correlation of error (for example, GPS-signal, satellite- 
ephemeris, receiver-clock, and atmospheric-propagation errors) between 
receivers, satellites, and epochs, or combinations thereof, to improve GPS 



NAVSTARGPS 8-47 



FM 3-34.331 



processing. Through differencing, the effects of the errors that are common to 
the observations being processed are greatly reduced or eliminated. There are 
three broad processing techniques that incorporate differencing— single, 
double, and triple. Differenced solutions generally proceed in the following 
order: differencing between receivers takes place first, between satellites 
second, and between epochs third. 



SINGLE DIFFERENCING 



8-188. There are three general single-differencing techniques— between 
receivers, between satellites, and between epochs. 

• Between receivers. Single differencing the mathematical models for 
pseudorange (C/A- or P-code) carrier-phase observable measurements 
between receivers will eliminate or greatly reduce satellite-clock 
errors and a large amount of satellite-orbit and atmospheric delays. 

• Between satellites. Single differencing the mathematical models for 
pseudorange or carrier-phase observable measurements between 
satellites will eliminate receiver-clock errors. Single differencing 
between satellites can be done at each individual receiver during 
observations as a precursor to double differencing and to eliminate 
receiver -clock errors. 

• Between epochs. Single differencing the mathematical models 
between epochs takes advantage of the Doppler shift (apparent 
change in the frequency of the satellite signal by the relative motion of 
the transmitter and the receiver). Single differencing between epochs 
is generally done in an effort to eliminate cycle ambiguities. Three 
forms of single-differencing techniques between epochs are— 
intermittently integrated Doppler (I I D), consecutive Doppler counts 
(CDC), and continuously integrated Doppler (CI D). 

I ID. IID is a technique whereby the Doppler count is recorded for 

a small portion of the observation period. The Doppler count is 

reset to zero and, then at a later time, the Doppler count is 

restarted during the observation period. 

CDC. CDC is a technique whereby the Doppler count is recorded 

for a small portion of the observation period. The Doppler count is 

reset to zero and then restarted immediately. 

CID. CID is a technique whereby the Doppler count is recorded 

continuously throughout the observation period. 



DOUBLE DIFFERENCING 



8-189. Double differencing is a differencing of two single differences. Double 
differencing eliminates clock errors. There are two general double-differencing 
techniques— receiver-time and receiver -satellite. 

• Receiver time. This technique requires the use of a change from one 
epoch to the next in the between-receiver single differences for the 
same satellite. This technique eliminates satellite-dependent integer- 
cycle ambiguities and simplifies the editing of cycle slips. 

• Receiver satellite. There are two techniques that can be used to 
compute a receiver-satellite double difference. One technique involves 



8-48 NAVSTARGPS 



FM 3-34.331 



using two between-receiver single differences and a pair of receivers 
that record different satellite observations between two satellites. The 
second technique involves using two between-satellite single 
differences and a pair of satellites, but different receivers, and then 
differences the satellite observations between the two receivers. 

TRIPLE DIFFERENCING 

8-190. The triple-differencing technique is called receiver-satellite time. All 
errors eliminated during single and double differencing are also eliminated 
during triple differencing. When used in conjunction with carrier-beat-phase 
measurements, triple differencing eliminates initial cycle ambiguity. During 
triple differencing, the data is automatically edited by the software to delete 
any data that is ignored during the triple-difference solution. This is 
advantageous because of the reduction in the editing of data required; 
however, degradation of the solution may occur if too much of the data are 
eliminated. 

BASELINE SOLUTION BY CYCLE-AMBIGUITY RECOVERY 

8-191. The resultant solution (baseline vector) that is produced from carrier- 
beat-phase observations when differencing resolves cycle ambiguity is called a 
"fixed" solution. The exact cycle ambiguity does not need to be known to 
produce a solution; if a range of cycle ambiguities is known, then a "float" 
solution can be formulated from the range of cycle ambiguities. It is desirable 
to formulate a fixed solution. However, when the cycle ambiguities cannot be 
resolved, which occurs when a baseline is between 20 to 65 kilometers, a float 
solution may actually be the best solution. The fixed solution may be unable to 
determine the correct set of integers (fix the integers) required for a solution. 
Double-difference fixed techniques can be effective for positional solutions 
over short baselines (less than 20 kilometers). Double-difference float 
techniques normally can be effective for positional solutions of medium-length 
lines (20 to 65 kilometers). 

DATA PROCESSING AND VERIFICATION 

8-192. Baselines should be processed daily in the field to identify any 
problems that may exist. Once baselines are processed, each baseline output 
file should be reviewed. The procedures used in baseline processing are 
manufacturer-specific. Certain computational items within the baseline 
output are common among manufacturers and may be used to evaluate the 
adequacy of the baseline observation in the field. The triple-difference float 
solution is normally listed. The geodetic azimuth and the distance between 
the two stations are also listed. The RMS is a quality factor that helps identify 
which vector solution (triple, float, or fixed) to use in the adjustment. The 
RMS is dependent on the baseline length and the length of baseline 
observation. Table8-6, page8-50, provides guidelines for determining the 
baseline quality. If the fixed solution meets the criteria in this table, the fixed 
vector should be used in the test. If the vector does not fit into the network 



NAVSTARGPS 8-49 



FM 3-34.331 



after adjustment, try using the float vector in the adjustments or check to 
make sure that the stations were occupied correctly. 



Table 8-6. Postprocessing Criteria 



Distance Between 
Receivers (km) 


RMS Criteria Formulation 
(d = Distance Between Receivers) 


Formulated RMS 
Range (Cycles) 


Formulated RMS 
Range (m) 


0-10 


<[0.02 + (0.0040 • d)] 


0.020 - 0.060 


0.004-0.012 


10-20 


<[0.03 + (0.0030 • d)] 


0.060 - 0.090 


0.012-0.018 


20-30 


<[0.04 + (0.0025 • d)] 


0.090-0.115 


0.018-0.023 


30-40 


<[0.04 + (0.0025 • d)] 


0.115-0.140 


0.023 - 0.027 


40-60 


<[0.08 + (0.0015 «d)] 


0.140-0.170 


0.027-0.032 


60-100 


<0.17 


0.170 


0.032 


>100 


<0.20 


0.200 


0.040 


NOTES: 

1. These are general postprocessing criteria that may be superseded by GPS receiver/software 
manufacturers' guidelines; consult those guidelines when appropriate. 

2. For lines longer than 50 kilometers, dual-frequency GPS receivers are recommended to meet 
these criteria. 



8-193. The first step in processing the data is to transfer the observation data 
to a storage device for archiving and/or further processing. The types of 
storage devices includea hard disc, a 3.5-inch diskette, or a magnetictape. 

8-194. Once observation data have been downloaded, preprocessing of the 
data can be completed. Preprocessing consists of smoothing and editing the 
data and ephemeris. Smoothing and editing ensures data quantity and 
quality. Smoothing and editing includes determining and eliminating cycle 
slips; editing gaps in information; and differencing between receivers, 
satellites, and epochs. 

8-195. Retrieval of postprocessed ephemerides may be required depending on 
the type of receiver used for the survey. Codeless receivers require a 
postprocessed ephemerides file. This file can be recorded by another GPS 
receiver concurrent with the survey or by postprocessed ephemerides provided 
by an ephemeris service. Code receivers do not require postprocessed 
ephemerides since they automatically record the broadcast ephemerides 
during the survey. 

8-196. Generally, postprocessing software will provide three solutions— a 
triple difference, a double-difference fixed solution, and a double-difference 
float solution. I n addition to RDOP as a measurement of the quality of data 
reduction, two methods that can be used to gauge the success of an 
observation session (based on data processing done by a differencing process) 
areRMSand repeata bi I i ty. 

• RMS. RMS is a measurement (in units of cycles or meters) of the 
quality of the observation data collected during a point in time. RMS 
is dependent on the line length, the signal strength, the ionosphere, 
the troposphere, and multipath effects. In general, the longer the line 
and the more signal interference by other electronic gear, the 



8-50 NAVSTARGPS 



FM 3-34.331 



ionosphere, the troposphere, and multipath effects, the higher the 
RMS will be. A good RMS factor (between 0.01 and 0.2 cycles) may not 
always indicate good results but should be considered. RMS can 
generally be used to judge the quality of the data used in 
postprocessi ng and the qual ity of the postprocessed basel i ne vector. 

• Repeatability. Redundant lines should agree to the level of accuracy 
that the GPS is capable of measuring. For example, if the GPS can 
measure a 10-kilometer baseline to 1 centimeter ±1 ppm, the expected 
ratio of misclosure would be as follows: 

1 cm ±1 ppm _1 cm ±1 ppm _0.01 m +0.01 m _ . ,„„ „„„ 
baseline 10 km 10,000 m 

Repeated baselines should be near the corresponding ratio. 

8-197. A baseline solution typically includes the foil owing information: 

The file name. 

The type of solution (single-, double-, or triple-difference). 

The satellites' avail ability during the survey for each station occupied. 

The ephemeris file used for the solution. 

The type of satellite selection (manual or automatic). 

The elevation mask. 

The minimum number of satellites used. 

Meteorological data (for example, pressure, temperature, or 

humidity). 

The session date and time. 

The data-logging start and stop time. 

Station information (for example, location [latitude, longitude, and 

height], the receiver's serial number, and the antenna's serial number 

and height). 

• The RMS. 

• The solution files (AX, AY, and AZ between stations, the slope distance 
between stations, Alatitude and Alongitude between stations, the 
horizontal distance between stations, and the height differences). 

• The epoch intervals. 

• The number of epochs. 

8-198. Sample static-baseline formulations are shown in Figure8- 7, 
page8-52. The baseline formulations compensate for the height differences 
between antennas. 



LOOP-CLOSURE CHECKS 



8-199. Postprocessing criteria are aimed at an evaluation of a single baseline. 
To verify the adequacy of a group of connected baselines, a loop closure must 
be performed on the established baselines. When G PS-baseline traverses or 
loops are formed, their linear (internal) closure should be determined in the 
field. If the job requires less than third-order accuracy (1:10,000 or 1:5,000) 
and the internal loop/traverse closures are very small, a formal (external) 
adjustment may not be warranted. 



NAVSTARGPS 8-51 



FM 3-34.331 









U.S. and NATO Military Forces 


Project Name: 




Belvoir 






Processed: 




Sunday, October 19, 1997 
WAVE 2. 10 


16:59 




Solution Output File (SSF): 




00000272.SSF 


IMPORTED 


From Station: 




DTP4 






Data file: 




DTP40722.DAT 






Antenna Height (meters): 




1.608 True Vertical 


1.618 Uncorrected 


Position Quality: 




Fixed Baseline Solution 






WGS 84 Position: 




38° 41' 23.838157" N 
77° 08' 03.891696" W 

6.725 




X 1109965.311 
Y -4859774.737 
Z 3965514.263 


To Station: 




FB09 






Data file: 




FB090722.DAT 






Antenna Height (meters): 




1.611 True Vertical 


1.621 Uncorrected 


WGS 84 Position: 




38° 41' 42.125849" N 
77° 08' • ">.A 1^00" W 




X 1108978.939 
Y -4859637.075 








Z 3965953.432 


Start Time: 


A 1 


3/ .V: M6:46:00.00 GPS 


(844 233160.00) 


Stop Time: 


*+<x 


3/12/96 17:50:15.00 GPS 


(844 237015.00) 


Occupation Time Meas. Interval ^ ... is.. 


01:04:15.00 


15.00 




Solution Type: 




LI fixed double difference 






Ephemeris: 




Broadcast 






Met Data: 




Standard 






Baseline Slope Distance Std. Dev. (meters): 


1088.462 


0.000185 








Forward 


Backward 


Normal Section Azimuth: 




301° 12' 27.087988" 


121° 12' 03.005418" 


Vertical Angle: 




-0° 05' 13.855491" 


0° 04' 38.662749" 


Baseline Components (meters): 




dx -986.371 dy 


137.662 


dz 439.169 


Standard Deviations (meters): 




0.000215 


0.000458 


0.000422 






dn 563.974 de 


-930.956 


du -1.656 






0.000174 


0.000166 


0.000613 

dh -1.563 
0.000613 


Aposteriori Covariance Matrix: 




4.6U597E-008 










-6.156637E-008 2.0977 16E-007 








4.545004E-008 -1.653685E-007 


1.777377E-007 


Variance Ratio: 




76.5 






Reference Variance: 




0.880 






Observable Count/Rejected 


RMS: 


LI phase 


1005/0 


0.004 



Figure 8-7. Sample Static-Baseline Formulations 



8-52 NAVSTARGPS 



FM 3-34.331 



LOOP-CLOSURE SOFTWARE 



8-200. The internal closure determines the consistency of the GPS 
measurements. Internal closures are applicable for loop traverses and GPS 
networks. It is required that one baseline in the loop be independent. An 
independent baseline is observed during a different session or different day. 
M any of the better postprocessing software packages come with a loop-closure 
program. Refer to the user's manual for the particulars of the loop-closure 
program. 



GENERAL LOOP-CLOSURE COMPUTATION 



8-201. If the postprocessing softwaredoes not contain a loop-closure program, 
the user can perform a loop-closure computation as described in the following 
steps. 

Step 1. List the AX, AY, AZ, and the distance components for all baselines 

used in the loop closure. 

Step 2. Sum the AX, AY, AZ, and the distance components for all baselines 

used in the loop closure. 

Step 3. Add the square of each of the summations together and then take the 

square root of this sum. This resultant value is the misclosure vector for the 

loop. 

Step 4. Calculate the loop-misclosure ratio as follows: 

t ■ i . m 

Loop-misclosure ratio = — 

where— 

m = misclosure vector for the loop 

L =total-loop distance (peri meter distance) 

8-202. The resultant value can be expressed as l:loop-misclosure ratio. All 
units for the expressions are stated in terms of the units used in the baseline 
formulations (for example, meters, feet, or millimeters). 



EXTERNAL CLOSURES 



8-203. External closures are computed in a manner similar to internal loops. 
External closures provide information on how well the GPS measurements 
conform to the local coordinate system. Before the closure of each traverse is 
computed, the latitude, the longitude, and the ellipsoid height must be 
converted to geocentric coordinates (X, Y, and Z). If the ellipsoid height is not 
known, geoid-modeling software can be used with the orthometric height to 
get an approximate ellipsoid height. The external closure aids in determining 
the quality of the known control and how well the GPS measurements 
conform to the local network. If the control stations are not of equal precision, 
the external closures will usually reflect the lower-order station. If the 
internal closure meets the requirements of the job but the external closure is 
poor, the known control is probably deficient and an additional known control 
point should be included in the system. 



NAVSTARGPS 8-53 



FM 3-34.331 



DATA ARCHIVAL 



8-204. The raw data is the data recorded during the observation period. Raw 
data should be stored on an appropriate medium (such as a floppy disk, a 
portable hard drive, or a magnetic tape). The raw data and the hard copy of 
the baseline reduction (resultant baseline formulations) should be stored at 
the discretion of each unit's command. 



SECTION VII - PRECISE-POSITIONING SURVEY ADJUSTMENTS 



8-205. Differential carrier-phase GPS-S observations are adjusted the same 
as conventional-survey observations. Each 3D G PS-baseline vector is treated 
as a separate distance observation and adjusted as part of a network. A 
variety of methods may be used to adjust the observed GPS baselines to fit 
existing control. Since GPS-S networks often contain redundant observations, 
they are usually adjusted by some type of a rigorous least-squares- 
minimization method. This section describes some of the methods used to 
perform horizontal GPS-S adjustments and provides guidance on evaluating 
the adequacy and accuracy of the adjustment results. 

GPS ERROR-MEASUREMENT STATISTICAL TERMS 

8-206. To understand the adjustment results of a GPS-S, some simple 
statistical terms are defined— 

• Accuracy. Accuracy is how close a measurement or a group of 
measurements are in relation to a true or known value. 

• Precision. Precision is how close a group or sample of measurements 
are to each other. For example, a low standard deviation indicates 
high precision. A survey or group of measurements can have a high 
precision but a low accuracy (for example, measurements are close 
together but not close to the known or true value). 

• Standard deviation. The standard deviation is a range of how close 
the measured values are from the arithmetic average. A low standard 
deviation indicates that the observations or measurements are close 
together. 



ADj USTMENT CONSIDERATIONS 



8-207. Although vertical elevations are necessarily carried through the 
baseline reduction and adjustment process, the relative accuracy of these 
elevations is normally inadequate for engineering and construction purposes. 
Special procedures and constraints are necessary to determine approximate 
orthometric elevations from relative GPS observations. 

8-208. The baseline-reduction process provides the raw relative-position 
coordinates that are used in a 3D GPS-network adjustment. I n addition, and 
depending on the software, each reduced baseline will contain various 
orientation parameters, covariance matrices, and cofactor and/or correlation 
statistics that may be used in weighting the final network adjustment. Most 
least-squares adjustments use the accuracy or correlation statistics from the 



8-54 NAVSTARGPS 



FM 3-34.331 



baseline reduction; however, other weighting methods may be used in a least- 
squares or approximate adjustment. 

8-209. The adjustment procedure employed (and the time devoted to it) must 
be commensurate with the project's accuracy requirements. Care must be 
taken to prevent the adjustment process from becoming a project in itself. 
There is no specific requirement for performing a rigorous least-squares 
adjustment on topographic surveys, whether conventional, GPS, or mixed 
observations. Traditional approximate-adjustment methods may be used in 
lieu of the least-squares method and will provide comparable, practical 
accuracy results. 

8-210. Commercial software packages designed for high-order geodetic- 
densification surveys often contain a degree of statistical sophistication that is 
unnecessary for engineering survey-control densification (for example, second- 
order or less). The distinction between geodetic surveying and engineering 
surveying must be fully considered when performing GPS-S adjustments and 
analyzing the results. 

8-211. Connections and adjustments to existing control networks, such as the 
NGRS, must not become independent projects. It is far more important to 
establish dense and accurate local-project control than to consume resources 
tying into first-order NGRS points that are miles from the project. 
Engineering, artillery, construction, and property/boundary referencing 
requires consistent local control with high relative accuracy. Accurate 
connections/references to distant geodetic datums are of secondary importance 
(exceptions are projects in support of military aviation operations). GPS- 
surveying technology has provided a cost-effective means of tying previously 
established, poorly connected projects to the NGRS and simultaneously 
transforming the project to the newly defined NAD 83. I n adjusting these 
connections, do not distort or warp long-established project reference points. 



SURVEY ACCURACY 



8-212. The accuracy of a survey (whether performed using conventional or 
GPS methods) is a measure of the difference between observed and true 
values (such as, coordinates, distance, or angle). Since the true values are 
rarely known, only estimates of survey accuracy can be made. These estimates 
may be based on the internal observation closures (such as on a loop traverse) 
or connections with previously surveyed points assumed to have some degree 
of reliability. 

8-213. GPS internal accuracies are typically far superior to most previous 
control networks (including the NAD-83 NGRS). Therefore, determining the 
accuracy of a GPS-S based on misclosures with external points is not always 
valid unless statistical-accuracy estimates (for example, station variance- 
covariance matrices or distance/azimuth relative accuracy estimates) from the 
external network's original adjustments are incorporated into the closure 
analysis for a new GPS-S. 

8-214. Most survey specifications and standards classify accuracy as a 
function of the resultant relative accuracy between two usually adjacent 
points in a network. This resultant relative accuracy is estimated from the 



NAVSTARGPS 8-55 



FM 3-34.331 



statistics in an adjustment and is defined by the size of a 2D or 3D relative 
error ellipse formed between the two points. Relative distance-, azimuth-, or 
elevation -accuracy specifications and classifications are derived from this 
model and are expressed either in absolute values (for example, ±1.2 
centimeters or +3.5 inches) or as ratios of the propagated standard errors to 
the overall length (for example, 1:20,000). 



INTERNAL ACCURACY 



8-215. A loop traverse that originates and ends from a single point will have a 
misclosurewhen observations (for example, EDM traverse angles/distances or 
G PS-baseline vectors) are computed forward around the loop and back to the 
starting point. The forward-computed mi sclosu re provides an estimate of the 
relative or internal accuracy of the observations in the traverse loop, or more 
directly, the internal precision of the survey. This is perhaps the simplest 
method of evaluating the adequacy of a survey. These point misclosures 
(usually expressed as ratios) are not the same as relative distance accuracies). 

8-216. Internal-accuracy estimates made relative to a single fixed point are 
obtained when free, unconstrained, or minimally constrained adjustments are 
performed. I n the case of a single loop, no redundant observations (or 
alternate loops) back to the fixed point are available. When a series of GPS- 
baseline loops (or networks) are observed, then the various paths back to the 
single fixed point provide multiple position computations. This allows for a 
statistical analysis of the internal accuracy of not only the position closure but 
also the relative accuracies of the individual points in the network (including 
relative distance- and azimuth-accuracy estimates between these points). The 
magnitude of these relative internal-accuracy estimates (on a free 
adjustment) determines the adequacy of the control for subsequent design, 
construction, and mapping work. 

8-217. Loop traverses are not recommended for most conventional surveys 
due to potential systematic distance or orientation errors, which can be 
carried through the network undetected. FGCS classification standards for 
geodetic surveys do not allow traverses to start and terminate at a single 
point. Such techniques are unacceptable for incorporation into the NGRS 
network. H owever, due to many factors (pri mari ly economic), loop traverses or 
open-ended spur lines arecommonly employed in densifying project control for 
engineering and construction projects. Since such control is not intended for 
inclusion in the NGRS and usually covers limited project ranges, these 
practices have been acceptable for GPS-Ss that are performed in support of 
similar engineering and construction activities. 



EXTERNAL ACCURACY 



8-218. The coordinates (and reference orientation) of a single, fixed starting 
point will also have some degree of accuracy relative to the network in which 
it is located (such as the NGRS if it was established relative to the system/ 
datum). This external accuracy (or inaccuracy) is carried forward in the 
traverse loop or network; however, any such external variance (if small) is 
generally not critical to engineering and construction projects. When a survey 
is conducted relative to two or more points on an existing reference network 
(such as project control or the NGRS), misclosures with these fixed control 



8-56 NAVSTARGPS 



FM 3-34.331 



points provide an estimate of the absolute accuracy of the survey. This 
analysis is usually obtained from a final adjustment (usually a fully 
constrained least-squares-minimization method) or by another recognized 
traverse-adjustment method (for example, a transit or a compass). 

8-219. This absolute accuracy estimate assumes that the fixed (existing) 
control is superior to the survey being performed and that any position 
misclosures at connecting points are due to internal observational errors and 
not the existing control. This has always been a long-established and practical 
assumption and has considerable legal basis in property/boundary surveying. 
New work is rigidly adjusted to existing control regardless of known or 
unknown deficiencies in the fixed network. 

8-220. Since the relative positional accuracies of points on the NGRS are 
known from the NAD-83 readjustment and G PS-baseline-vector accuracy 
estimates are obtained from individual reductions, variations in misclosures 
in GPS-Ssarenot always due totally to errors in theGPS work. Forcing a GPS 
traverse/network to rigidly fit the existing (fixed) network usually results in a 
degradation of the internal accuracy of the GPS-S, as compared with a free or 
unconstrained adjustment. 

INTERNAL VERSUS EXTERNAL ACCURACY 

8-221. Conventional geodetic surveying is largely concerned with absolute 
accuracy or the best fit of intermediate surveys between points on a national 
control network, such as the NGRS. Alternatively, in engineering and 
construction surveying and to a major extent in relative- or local-boundary 
surveying, accuracies are more critical to the project at hand. Thus, the 
absolute NAD-27 or NAD-83 coordinates (in latitude and longitude) relative to 
the NGRS datum reference are of less importance; however, accurate relative 
coordinates for a given project are critical to design and construction. 

8-222. For example, when establishing basic mapping and construction- 
layout control for a military installation, developing a dense and accurate 
internal relative-control network is far more important than considering the 
values of the coordinates relative to the NGRS. Surveys performed with GPS- 
S, and the final adjustment thereof, should be configured/designed to 
establish accurate relative (local) project control. This is of secondary 
importance in connection with NGRS networks. 

8-223. Although reference connections with the NGRS are desirable and 
recommended and should be made where feasible and practicable, it is critical 
that such connections (and subsequent adjustments thereto) do not distort the 
internal accuracy of intermediate points from which design, construction, or 
project boundaries are referenced. Connections and adjustments to distant 
networks (for example, NGRS) can result in mixed datums within a project 
area, especially if not all existing project control has been tied in. This can 
lead to errors and contract disputes during both design and construction. On 
existing projects with long-established reference control, connections and 
adjustments to outside reference datums/networks should be performed with 
caution. The impacts on legal-property and project-alignment definitions must 
also be considered before such connections. 



NAVSTARGPS 8-57 



FM 3-34.331 



8-224. On newly authorized projects or on projects where existing project 
control has been largely destroyed, reconnection with the NGRS is highly 
recommended. This will ensure that future work is supported by a reliable 
and consistent basic network, while minimizing errors associated with mixed 
datums. 



ADj USTMENTS 



8-225. GPS-Ss are usually adjusted and analyzed relative to their internal 
consistency and external fit with existing control. The internal-consistency 
adjustment (for example, free or minimally constrained) is important from a 
mission compliance standpoint. The final (or constrained) adjustment fits the 
GPS-S to the existing network. This is not always easily accomplished since 
existing networks often have lower relative accuracies than the GPS 
observations being fit. The evaluation of a survey's adequacy should not be 
based solely on the results of a constrained adjustment. 



INTERNAL ADJ USTMENT 



8-226. An internal (or geometric) adjustment (also referred to as a free 
adjustment) is made to determine how well the baseline observations close 
internally or fit within themselves. Other EDM distances or angles may also 
be included in the adjustment. This adjustment provides a measure of the 
internal precision of the survey. 

8-227. In a simplified example, a conventional EDM traverse that is looped 
back to the starting point will misclose in both azimuth and position. 
Conventional approximate-adjustment methods will typically assess and 
proportionately adjust the azimuth misclosure (usually evenly per station), 
recompute the traverse with the adjusted azimuths, and obtain a position 
misclosure. This position misclosure (in X and Y) is then distributed among all 
the points on the traverse using various weighting methods (for example, 
distance, latitudes, or departures). Final-adjusted azimuths and distances are 
then computed from grid inverses between the adjusted points. The adequacy/ 
accuracy of such a traverse is evaluated based on the azimuth misclosure and 
the position misclosure after the azimuth adjustment (usually expressed as a 
ratio to the overall length of the traverse). 

8-228. A least-squares adjustment of the same conventional loop traverse will 
end up adjusting the points similarly to the approximate methods 
traditionally employed. The only difference is that a least-squares adjustment 
simultaneously adjusts both the observed angles (or directions) and the 
distance measurements. A least-squares adjustment also allows variable 
weighting to be set for individual angle/distance observations, which is a 
somewhat more complex process when approximate adjustments are 
performed. In addition, a least-squares adjustment will yield more definitive 
statistical results of the internal accuracies of each observation and/or point, 
rather than just the final closure. This includes estimates of the accuracies of 
individual station coordinates, relative azimuths, and relative distances. 

8-229. A series of GPS baselines forming a loop off a single point can be 
adjusted and assessed similarly to a conventional-EDM traverse loop 
described above. The baseline-vector components may be computed 



8-58 NAVSTARGPS 



FM 3-34.331 



(accumulated) around the loop with a resultant 3D misclosure back at the 
starting point. These mi sclosu res (in X, Y, and Z) may be adjusted using either 
approximateor least-squares methods. The method by which the misclosure is 
distributed among the intermediate points in the traverse is a function of the 
weighting adjustment. 

8-230. I n the case of a simple E DM traverse adjustment, the observed 
distances (or position corrections) are weighted as a function of the segment 
length and the overall traverse length or the overall sum of the latitudes/ 
departures (transit rule). Two-dimensional EDM distance observations are 
not dependent on their direction (a distance's X and Y components are 
uncor related). 

8-231. G PS-baseline-vector components (in X, Y, and Z) are correlated due to 
the geometry of the satellite solution (the direction of the baseline vector is 
significant). Since satellite geometry is continuously changing, remeasured 
baselines will have different correlations between the vector components. 
Such data are passed down from the baseline-reduction software for use in the 
adjustment. 

8-232. The magnitude of the misclosure of the GPS-baseline vectors at the 
initial point provides an estimate of the internal precision or geometric 
consistency of the loop (survey). When this misclosure is divided by the overall 
length of the baselines, a relative internal-accuracy estimate results. This 
misclosure ratio should not be less than the relative distance accuracy 
intended for the survey. For example, if the position misclosure of a GPS loop 
is 0.08 meter and the length of the loop is 8,000 meters, then the loop closure 
is 0.08 divided by 8,000, which equals 1:100,000. 

8-233. When an adjustment is performed, the individual corrections/ 
adjustments made to each baseline (so-called residual errors) provide an 
accuracy assessment for each baseline segment. A least-squares adjustment 
can also provide relative distance-accuracy estimates for each line, based on 
the standard-error propagation between the adjusted points. This relative 
distance-accuracy estimate is most critical in engineering and construction 
work and represents the primary basis for assessing the acceptability of a 
survey. 



EXTERNAL ADJ USTMENT 



8-234. An external (or fully-constrained) adjustment is the process used to 
best fit the survey observations to the established reference system. The 
internal, free adjustment provides adjusted positions relative to a single, often 
arbitrary, fixed point. Most conventional or GPS-Ss are connected between 
existing stations on some predefined reference network or datum. These fixed 
stations may be existing project-control points (on NAD 27) or stations on the 
NGRS (NAD 83). In OCONUS locales, other local or regional reference 
systems may be used. 

8-235. A simple, conventional-EDM traverse between two fixed stations best 
illustrates the process by which comparable GPS-baseline vectors are 
adjusted. As with the loop traverse, the misclosure in azimuth and position 
between the two fixed points may be adjusted by any type of approximate or 
least-squares-adjustment method. Unlike a loop traverse, however, the 



NAVSTARGPS 8-59 



FM 3-34.331 



azimuth and position misclosures are not wholly dependent on the internal 
errors in the traverse— the fixed points and their azimuth references are not 
absolute but contain relative inaccuracies with respect to one another. 

8-236. A GPS-S between the same two fixed points also contains a 3D position 
misclosure. Due to positional uncertainties in the two fixed points, this 
misclosure may (and usually does) far exceed the internal accuracy of the raw 
GPS observations. As with a conventional-EDM traverse, the 3D misclosures 
may be approximately adjusted by proportionately distributing them over the 
intermediate points. A least-squares adjustment will also accomplish the 
same thing. 

8-237. For example, if a GPS-S is looped back to the initial point, the free- 
adjustment misclosure at the initial point may be compared with the 
apparent-position misclosure at the other fixed point. A free-adjustment loop 
misclosure is 1:100,000, whereas the misclosure relative to the two network- 
control points is only 1:5,000. Thus, the relative internal accuracy of a GPS-S 
is about 1:100,000 (based on the misclosure). If the G PS-baseline observations 
are constrained to fit the existing control, the 0.6-meter external misclosure 
must be distributed among the individual baselines to force a fit between the 
two end points. 

8-238. After a constrained adjustment, the absolute-position misclosure of 
0.6 meter causes the relative distance accuracies between individual points to 
degrade. They will be somewhat better than 1:5,000 but far less than 1:10,000. 
The statistical results from a constrained least-squares adjustment will 
provide estimates of the relative accuracies between individual points on the 
traverse. 

8-239. This example illustrates the advantages of measuring the baseline 
between fixed network points when performing GPS-Ss, especially when weak 
control is suspected. Also illustrated is the need for making additional ties to 
the existing network. In this example, one of the two fixed points was poorly 
controlled when it was originally established or the two points may have been 
established from independent networks (for example, were never connected). 
A third or even fourth fixed point would be beneficial in resolving such a case. 

8-240. If the intent of the survey in this example was to establish 1:20,000 
relative-accuracy control, connecting between these two points would not 
provide that accuracy, given the amount of adjustment that must be applied 
to force a fit. For example, if one of the individual baseline vectors was 
measured at 600 meters and the constrained adjustment applied a 0.09-meter 
correction in this sector, the relative accuracy of this segment would be 
roughly 1:6,666. This distortion is not acceptable for subsequent design/ 
construction work. 

8-241. Most GPS-S networks are more complex than a simple traverse. They 
may consist of multiple loops and may connect with any number of control 
points on the existing network. In addition, conventional E DMs and 
differential -leveling and angle measurements may be included with the GPS 
baselines, resulting in a complex network with many adjustment conditions. 



8-60 NAVSTARGPS 



FM 3-34.331 



PARTIALLY CONSTRAINED ADJ USTMENTS 



8-242. I n the previous example of a simple GPS traverse, holding the two 
network points rigidly caused an adverse degradation in theGPS-S because of 
the differences between the free (loop) adjustment and the fully constrained 
adjustment. Another alternative is to perform a partially constrained 
adjustment of the network. In a partially constrained adjustment, the two 
network points are not rigidly fixed but are only partially fixed in position. 
Partially constrained adjustments are not practicable using approximate- 
adjustment methods. 

8-243. For example, if the relative distance accuracy between the two fixed 
points is about 1:10,000, it can be equated to a positional uncertainty between 
these points. Depending on the type and capabilities of the least-squares- 
adjustment software, the higher-accuracy GPS-baseline observations can be 
best fit between the two end points, such that the end points of the GPS 
network are not rigidly constrained to the original two control points but end 
up falling near them. 

8-244. Adjustment software allows relative weighting of the fixed points to 
provide a partially constrained adjustment. Any number of fixed points can be 
connected, and these points may be given partial constraints in the 
adjustment. Performing partially constrained adjustments (as opposed to fully 
constrained adjustments) takes advantage of the inherent higher-accuracy 
GPS data relative to the existing network control. Less warping of the GPS 
data (due to poor existing networks) will occur. 

8-245. A partial constraint also lessens the need for performing numerous 
trial-and-error constrained adjustments in attempts to locate poor external 
control points causing high residuals. Fewer ties to the existing network are 
needed if the purpose of such ties is to find a best fit on a fully constrained 
adjustment. 

8-246. When connections are made to NAD 83, relative accuracy estimates of 
NGRS stations can be obtained from the NGS. Depending on the type of 
adjustment software, these partial constraints may be in the form of variance- 
covariance matrices, error ellipses, or circular accuracy estimates. 



RIGOROUS LEAST-SQUARES ADJ USTMENT 



8-247. Adjustment of GPS networks on PCs is typically a trail-and-error 
process for both the free and the constrained adjustments. When a least- 
squares adjustment is performed on a network of GPS observations, the 
adjustment software will provide 2D- or 3D-coordinate accuracy estimates, 
variance-covariance matrix data for the adjusted coordinates, and related 
error-ellipse data. Most software programs provide relative accuracy 
estimates (length and azimuth) between points. Analyzing these various 
statistics is not easy, and they are also easily misinterpreted. Arbitrary 
rejection and readjustment to obtain a best fit must be avoided. The original 
data-reject criteria must be established and justified in a final report. 

8-248. When a series of loops are formed relative to a fixed point or off 
another loop, different redundant conditions are formed (this is comparable to 
loops formed in conventional-differential leveling networks). These different 



NAVSTARGPS 8-61 



FM 3-34.331 



loops allow forward baseline-vector position computations to be made over 
different paths. From the different routes (loops) formed, different positional 
closures at a singlefixed point results. These variances in position misclosures 
from the different routes provide additional data for assessing the internal 
consistency of the network, in addition to checking for blunders in the 
individual baselines. The number of different paths, or conditions, is partially 
related to the number of degrees of freedom in the network. 

8-249. M ultiple baseline observations provide additional redundancy or 
strength to a line or network since they are observed at two distinct times of 
varying satellite geometry and conditions. The amount of redundancy 
required is a function of the accuracy requirements of the survey. Performing 
a free adjustment on a complex network containing many redundancies is best 
performed using a least-squares method. Approximate-adjustment methods 
are difficult to evaluate when complex interweaving networks are involved. 

8-250. Baseline-reduction vector-component error statistics are usually 
carried down into a least-squares adjustment; however, their use is not 
mandatory for lower-order engineering surveys. GPS-network least-squares 
adjustments can be performed without all the covariance and correlation 
statistics from the baseline reduction. 

8-251. I n practice, any station on the network can be held fixed for all three 
coordinates, along with the orientation of the three axes and a network-scale 
parameter. Usually one of the higher-order points on the existing network is 
used. 

8-252. Least-squares-adjustment software will output various statistics from 
the free adjustment to assist in detecting blunders and residual outliers in the 
free adjustment. Most commercial packages will display the normalized 
residual for each observation (for example, GPS, EDM, angle, or elevation), 
which is useful in detecting and rejecting residual outliers. The variance of 
unit weight is also important in evaluating the overall adequacy of the 
observed network. Other statistics (such as chi-square, confidence levels, or 
histograms) are usually not significant for lower-order engineering projects 
and become totally insignificant if the user is not well versed in statistics and 
adjustment theory. The use of these statistics to reject data (or to report the 
results of an adjustment) without fully understanding their derivation and 
source within the network adjustment is not advised. 

8-253. Relative positional- and distance-accuracy estimates resulting from a 
free adjustment of a GPS network are usually excellent in comparison to 
conventional surveying methods. Loop misclosures and relative distance 
accuracies between points commonly exceed 1:100,000. Relative distance- 
accuracy estimates between points in a network are determined by error 
propagation in the relative positional standard errors at each end of the tie. 
Relative accuracy estimates may be derived for resultant distances or 
azimuths between the points. The relative distance-accuracy estimates are 
those typically employed to assess the free and constrained accuracy 
classifications, expressed as a ratio (such as 1:80,000). Since each point in the 
network has its particular position variances, the relative distance accuracy 
propagated between any two points will also vary throughout the network. 



8-62 NAVSTARGPS 



FM 3-34.331 



8-254. The minimum value (or the largest ratio) will govern the relative 
accuracy of the overall project. This minimum value (from a free adjustment) 
is compared with the intended relative accuracy classification of the project to 
evaluate compliance. However, relative distance-accuracy estimates should 
not be rigidly evaluated over short lines (less than 500 meters). 

8-255. Depending on the size and complexity of the project, large variances in 
the propagated relative distance accuracies can result. When a constrained 
adjustment is performed, the adequacy of the external fixed stations will have 
a major impact on the resultant and propagated distance accuracies, 
especially when connections are made to weak control systems. Properly 
weighted, partially constrained adjustments will usually improve the 
propagated distance accuracies. 

8-256. The primary criteria for assessing the adequacy of a particular GPS-S 
is the relative distance-accuracy results from a minimally constrained free 
adjustment, not a fully constrained adjustment. This is due to the difficulty in 
assessing the adequacy of the surrounding network. I f the propagated relative 
accuracies fall below the specified level, then reobservation is warranted. 

8-257. If the relative distance accuracies significantly degrade the 
constrained adjustment (due to the inadequacy of the surrounding network), 
any additional connections to the network would represent a change in 
contract scope. A large variance of unit weight usually results in such cases. 

8-258. If only approximate adjustments are performed, then the relative 
distance accuracies may be estimated as a function of the loop or position 
misclosure or the residual corrections to each observed length. For example, if 
a particular loop or line miscloses by 1:100,000, then individual-baseline 
relative accuracies can be assumed to be adequate if only a 1:20,000 survey is 
required. 

8-259. Most adjustment software will output the residual corrections to each 
observed baseline- vector component. These residuals indicate the amount 
that each segment was corrected in the adjustment. A least-squares 
adjustment minimizes the sum of the squares of these baseline residual 
corrections. 

8-260. Commercial least-squares-adjustment software is available, which will 
adjust GPS networks using standard PCs. An example of an adjustment 
statistics summary from the software package used by Army topographic 
surveyors is shown in Figure8-8, page8-64. 

8-261. Relative GPS-baseline standard errors can be obtained from the 
baseline-reduction output and in some software programs can be directly 
input into the adjustment. These standard errors, along with their 
correlations, are given for each vector component (X, Y, and Z). They are 
converted to relative weights in the adjustment. The following typical input 
(a priori) weighting is commonly used: 

• Fixed. +3 millimeters (latitude) +5 millimeters (longitude) + 1 ppm 
+10 millimeters (height) +1 ppm. 

• Float. +6 millimeters (latitude) +10 millimeters (longitude) +2 ppm 
+10 millimeters (height) +2 ppm. 



NAVSTARGPS 8-63 



FM 3-34.331 



ADJUSTMENT STATISTICS SUMMARY 

NETWORK = Belvoir 

TIME = Mon Oct 20 20:20:26 1997 



ADJUSTMENT SUMMARY 



Network Reference Factor = 0.88 
Chi-Square Test {a = 95%) = PASS 

Degrees of Freedom = 105.00 



GPS OBSERVATIONS 

Reference Factor = 0.8 8 

r = 105.00 



GPS 


Solution 


1 


Reference 


Factor = 


1 


11 


GPS 


Solution 


2 


Reference 


Factor = 





37 


GPS 


Solution 


3 


Reference 


Factor = 


1 


41 


GPS 


Solution 


4 


Reference 


Factor = 


1 


58 


GPS 


Solution 


5 


Reference 


Factor - 


# 


-o 


GPS 


Solution 


6 


Reference 


r i Ijjw% f 


XI 


i3 


GPS 


Solution 


7 


Reference 


Fac%aK{ 


3^ 


70 


GPS 


Solution 


8 


Reference 


Factor ■ 


^"o 


55 


""" 


Ssl'Jt-i on 


Q 


•->- * 


^ ^ n *" r^^^.'; 




9^ 


opb 


bOlUtiwa 


1 J 


is.CiCXiiiiCC 


i-*^ucwir - 





5i 


GPS 


Solution 


48 


Reference 


Factor = 





71 



2.71 
2.97 



WEIGHTING STRATEGIES: 

GPS OBSERVATIONS: 

Scalar Weighting Strategy: 
User-Defined Scalar Set Applied Globally = 11. 



No summation weighting strategy was used 

Station Error Strategy: 
H.I. error = 0.0020 



ESC-EXIT ti=SCR0LL 
COORDINATE ADJUSTMENT SUMMARY 
NETWORK = Belvoir 
TIME - Mon Oct 20 20:20:26 1997 



PgUp 



PgDn 



Datum = WGS-84 
Coordinate System 
Zone = Global 



Geographic 



Network Adjustment Constraints: 
Inner constraints in y 
Inner constraints in x 
Inner constraints in H 



POINT NAME 

1 DTP4 

LAT= 

LON= 

ELL HT= 

ORTHO HT= 

2 FB09 

LAT= 

LON= 

ELL HT= 

ORTHO HT= 



OLD COORDS 



NEW COORDS 



38< 
77 < 



38° 
77° 



41' 
08' 



41 ' 
08 ' 



23.839155" 

03.890845" 

6.7551m 

. 0000m 



42.126953" 

42.414329" 

5. 1959m 

. 0000m 



+0.000007" 

+0. 000017" 

+0 .0062m 

+ .0000m 



-0.000003" 

-0.000003" 

+0 . 0008m 

+0. 0000m 



38' 
77' 



36° 
77° 



41' 23.839163" 

08' 03.890828" 
6.7613m 
0.0000m 



41 

08 



42.126950" 

42.414331" 

5.1967m 

.0000m 



1.96a 



0.002593m 
0.002305m 
0.005981m 
NOT KNOWN 



0.002604m 
0.002182m 
0.005981m 
NOT KNOWN 



Figure 8-8. Continuation of an Adjustment Statistics Summary Example 



8-64 NAVSTARGPS 



FM 3-34.331 



These optimum standard errors have been found to be reasonable in standard 
work where extremely long baselines are not involved. The use of these 
optimum values is recommended for the first adjustment iteration. 

8-262. The adequacy of the initial network weighting described above is 
indicated by the variance of unit weight, which equals the square of the 
standard error of unit weight. The variance of unit weight should range 
between 0.5 and 1.5 (or the standard error of unit weight should range 
between 0.7 and 1.2) with an optimum value of 1, signifying the realistic 
weighting of the GPS-input observations. A large unit variance (for 
example, 5) indicates that the initial GPS standard errors were too optimistic 
(low). A low unit variance (for example, 0.1) indicates that the results from the 
adjustment were better than the assumed GPS-baseline precisions. This unit- 
variance test, however, is generally valid only when a statistically significant 
number of observations are involved. This is a function of the number of 
degrees of freedom shown on the adjustment. To calculate the adequacy of a 
unit weight, a test (such as chi-square) is performed. Failure of such a test 
indicates that the variance factor may not be valid. 

8-263. The input standard errors can easily be juggled to obtain a variance of 
unit weight near 1. This trial-and-error technique is generally not a good 
practice. If the input weights are changed, they should not be modified beyond 
reasonable levels (for example, do not input a GPS standard error of 
+50 +50 ppm to get a good unit variance). If input standard errors are 
modified, these modifications should bethesamefor all lines, not just selected 
ones. Any such modifications of a priori standard errors must be justified in 
the adjustment report. 

8-264. Changing the magnitude of the input standard errors or weights will 
not change the adjusted position or residual results in a free adjustment, 
provided all weight changes are made equally. Although the reference 
variance will change, the resultant precisions (relative line accuracies) will 
not change (this is not true in a constrained adjustment). Therefore, the 
internal accuracy of a survey can be assessed based on the free-adjustment 
line accuracies regardless of the initial weighting or variance of unit weight. 

8-265. The magnitude of the residual corrections may be assessed by looking 
for blunders or outliers; however, this assessment should be performed in 
conjunction with the related, normalized- or standardized-residual statistic. 
This statistic is obtained by multiplying the residual by the square root of the 
input weight (the inverse of the square of the standard error). If the 
observations are properly weighted, the normalized residuals should be 
around 1. Most adjustment software will flag normalized residuals that 
exceed selected statistical outlier tests. Such residuals are candidates for 
rejection. As a rule of thumb, reject criterion should beset at three times the 
standard error of unit weight, provided that the standard error of unit weight 
is within the acceptable range given above. All rejected GPS observations 
must be justified in the adjustment report, and the test used to remove the 
observation from the file must be clearly described. 

8-266. Error ellipses, or 3D error ellipsoids, generated from the adjustment 
variance-covariance matrices for each adjusted point are also useful in 
depicting the relative positional accuracy. The scale of the ellipse may be 



NAVSTARGPS 8-65 



FM 3-34.331 



varied as a result of the 2-deviation function. A 2.45 sigma (or 95 percent) 
probability ellipse is usually selected for output. The size of the error-ellipse's 
relative distance or the azimuth-accuracy estimate between two adjacent 
points is a direct function of the size of these positional ellipses. 

8-267. The relative distance accuracy is used to evaluate the acceptability of a 
survey. This is done using a free adjustment. The output is shown as a ratio or 
in ppm. The resultant ratios must be divided by 2 to equate them to FGCS 
95 percent criteria. Further details on these statistical evaluations are beyond 
the scope of this manual. 

8-268. The following is a summary of a network-adjustment sequence 
(recommended by theNGS) for surveys that are connected with the NGRS: 

• A minimally constrained 3D adjustment is performed initially as a 
tool to validate the data, to check for blunders and systematic errors, 
and to look at the internal consistency of the network. 

• A horizontally constrained 3D adjustment is performed by holding all 
previously published horizontal-control points fixed and using one 
height constraint. All previous observations are considered in the 
adjustment. 

• A fully constrained vertical adjustment is performed to determine the 
orthometric heights. All previously published BM elevations are held 
fixed along with one horizontal position in a 3D adjustment. Geoid 
heights are predicted using the latest model. 

• A final free adjustment is performed and the relative accuracy 
esti mates are computed. 

EVALUATION OF ADj USTMENT RESULTS 

8-269. A survey shall be classified based on its horizontal-point closure ratio 
or its vertical-elevation-difference closure standard (Table8-7). 

HORIZONTAL-CONTROL STANDARDS 

8-270. The horizontal-point closure is determined by dividing the linear- 
distance misclosure of the survey into the overall circuit length of a traverse, 
loop, or network line/circuit. When independent directions or angles are 
observed (for example, a conventional survey [traverse or triangulation]), 
these angular misclosures may be distributed before assessing positional 
misclosure. I n cases where GPS vectors are measured in geocentric 
coordinates, the 3D positional misclosure is assessed. 

Approximate Surveying 

8-271. Approximate surveying is classified based on the survey's estimated or 
observed positional errors. This includes absolute GPS and some DGPS 
techniques with positional accuracies ranging from 10 to 150 feet (2-deviation 
RMS). There is no order of classification for approximate work. 



8-66 NAVSTARGPS 



FM 3-34.331 



Table 8-7. Point-Closure Standards for Horizontal- 
Vertical-Control Surveys 



and 



Horizontal 


Classification 


Point-Closure Standard (Ratio) 


Second order, Class I 


1 :50,000 


Second order, Class II 


1:20,000 


Third order, Class I 


1:10,000 


Third order, Class II 


1 :5,000 


Fourth order (construction layout) 


1 :2,500 - 1 :20,000 


Vertical 


Classification 


Point-Closure Standard (mm) 


Second order, Class I 




6Vdistance in km 


Second order, Class II 




87distance in km 


Third order 




12Vdistance in km 


Fourth order (construction layout) 




247distance in km 



High-Order Surveys 

8-272. Requirements for relative line accuracies exceeding 1:50,000 are rare 
for most applications. Surveys requiring accuracies of f i rst-order (1:100,000) 
or better, should be performed using FGCS standards and specifications and 
must be adjusted bytheNGS. 

Construction Layout or Grade Control (Fourth-Order) 

8-273. This classification is intended to cover temporary control used for 
alignment, grading, and measurement of various types of construction and 
some local site-plan topographic-mapping or photo-mapping control work. 
Accuracy standards will vary with the type of construction. Lower accuracies 
(1:2,500 to 1:5,000) are acceptable for earthwork, dredging, grading, and some 
site-plan stakeouts. Moderate accuracies (1:5,000) are used in most pipelines, 
sewers, culverts, catch basins, and manhole stakeouts; general residential- 
building foundation and footing construction; major highway pavement; and 
concrete-runway stakeouts. Somewhat higher accuracies (1:10,000 to 
1:20,000) are used for aligning longer bridge spans, tunnels, and large 
commercial structures. For extensive bridge or tunnel projects, 1:50,000 (or 
even 1:100,000) relative-accuracy alignment work may be required. Vertical 
grade is usually observed to the nearest 0.005 meter for most construction 
work, although 0.04-meter accuracy is sufficient for riprap placement, 
grading, and small-diameter-pipe placement. Construction control points are 
typically marked by semipermanent or temporary monuments (for example, 
plastic hubs, nails, or wooden grade stakes). Control may be established by 
short, nonredundant spur shots, using total stations or the GPS, or by single 
traverse runs between two existing, permanent control points. Positional 
accuracy will be commensurate with, and relative to, that of the existing 
point(s) from which the new point is established. 



NAVSTARGPS 8-67 



FM 3-34.331 



VERTICAL-CONTROL STANDARDS 



8-274. The vertical accuracy of a survey is determined by the elevation 
misclosure within a level section or level loop. For differential or trigonometric 
leveling, section or loop misclosures (in millimeters) shall not exceed the 
limits shown in Table8-7, page8-67, where the line or circuit length is 
measured in kilometers. Fourth-order accuracies are intended for 
construction-layout grading work. Procedural specifications or restrictions 
pertaining to vertical -control surveying or equipment should not be over 
restrictive. 



FINAL-ADj USTMENT REPORTS 



8-275. A variety of free- and/or constrained-adjustment combinations may be 
specified for a GPS-S. Specific stations to be held fixed may be indicated, and 
when they are partially constrained, appropriate statistical information must 
be provided. Either variance-covariance matrices or relative positional- 
accuracy estimates may be converted as approximate variance-covariance 
matrices in the constrained adjustment. All rejected observations will be 
clearly indicated, along with the criteria and the reason used for the rejection. 

8-276. When different combinations of constrained adjustments are 
performed due to indications of one or more fixed stations causing undue 
biasing of the data, an analysis should be made as to a recommended solution 
that provides the best fit for the network. Any fixed control points that should 
be readjusted to anomalies from theadjustment(s) should be clearly indicated 
in a final recommendation. 

8-277. The final -adjusted horizontal- and/or vertical -coord in ate values are 
assigned an accuracy classification based on the adjustment statistical 
results. This classification should include the resultant geodetic or Cartesian 
coordinates and the baseline-differential results. The final-adjusted 
coordinates should state the 95 percent confidence region of each point and 
the accuracy in ppm between all points in the network. The datum will be 
clearly identified for all coordinate listings. 

8-278. Final-report coordinate listings may be required on hard copy as well 
as specified computer media. A scaled plot should be submitted with the 
adjustment report showing the proper locations and designations of all 
stations established. 



8-68 NAVSTARGPS 



Chapter 9 

Artillery Surveys 

Topographic-engineer companies are the primary source of topographic 
support throughout the echelons above corps (EAC) and GS. Topographic 
companies support artillery surveys by— 

• Extending horizontal and vertical control into the corps and division 
areas. 

• Providing a survey planning and coordination element (SPCE) in 
support of the EAC. 

• Providing mapping-survey control where required. 

• Advising on topographic matters. 

• Assisting in lower-level surveys to augment FA surveys. 

This chapter defines topographic-survey-operation terms for precise 
positioning and orientation at division, corps, EAC, and joint-level 
commands for support of FA and ADA. The accuracy, timeliness, and 
distribution of positioning and orientation information and organic 
equipment are also addressed. 



US ARMY FA 



ACCURACY 



9-1. The FA is a primary user of precise-positioning and -orientation 
information in a wartime environment. Topographic-survey support must be 
provided to MLRS units, corps's GS units, and other nondivisional assets in 
the corps area. The FA requires that topographic surveyors— 

• Establish and recover monumented SCPs (horizontal and vertical) 
and azimuthal references for conventional and inertial FA survey 
teams. 

• Coordinate the exact position of the high-order control with the corps's 
survey officer. 

• Augment FA survey sections when appropriate. 



9-2. Established SCPs provide the FA a horizontal, vertical, and azimuthal 
reference. The horizontal and vertical coordinates and the azimuthal 
reference station must satisfy FGCS standards and specifications for third- 
order conventional and satellite positioning. 



FREQUENCY AND TIMELINESS 



9-3. The FA requires that initial SCPs be established within 5 kilometers of 
division artillery (Dl VARTY) and TA battery (TAB) surveyor's HQ. I n 
addition, a common grid must be established for theAO and should include an 



Artillery Surveys 9-1 



FM 3-34.331 



SCP and azimuthal reference every 30 kilometers. I n a wartime scenario, 
SCPs and azimuthal references are to be established within 30 minutes of 
notification. Topographic surveyors are required to establish third-order SCPs 
for the beginning and ending points for each PADS traverse used by MLRS 
and FA units. The distance interval between these SCPs should be 25 to 30 
kilometers throughout the division or the corps area. A precise GPS-S is the 
only expedient way to emplace third-order SCPs over this distance. The 
number of SCPs that a topographic survey must provide for the EAC and 
corps areas depend on the dispersion, the amount of movement, and the 
commander's priorities. For example, on the basis of five to seven moves per 
day, 10 to 20 SCPs will be required every 24 hours to support EAC and corps 
FA systems that the DIVARTY cannot support. 



DISTRIBUTION 



ADA 



9-4. The coordinates that topographic surveyors establish for the FA should 
be disseminated to the SPCE. The SPCE is the FA's counterpart to a SIC. 
SPCEs will be located at HQ and HQ battery (HHB) DIVARTY, corps, 
brigade, and MLRS battalions. If the SPCE is not in operation, the survey 
information should be distributed to the operations section S3 or the Assistant 
Chief of Staff, G3 (Operations and Plans) (G3) of the highest element 
(battalion, brigade, division, or corps). N I M A is many years away from 
publishing all maps on the WGS 84, therefore, the commander must be aware 
of all datums within the AO. Topographic surveyors are responsible for 
notifying the SPCE or the appropriate operations section of the various 
datums within theAO. In addition, topographic surveyors should provide the 
SPCE with the necessary parameters required to transform local coordinates 
to the predefined common grid (for example, WGS 84). Since paper map 
products will not be on a common datum (WGS 84) for many years, it is 
imperative that topographic surveyors identify these local datum and provide 
the FA with the necessary transformation parameters. Since map sheets may 
be on various local datums (for example, Bosnia, Hungry, or Saudi Arabia), 
the forward observers (FOs) and the weapon may be on a separate datum. The 
coordinate differences between datums may be hundreds of meters and 
positional differences may cause friendly-fire casualties or missed targets. 



9-5. The ADA requires positioning and orientation information. The ADA and 
the FA have agreed that FA surveyors (MOS 82C) will provide the ADA with 
survey support, to include the following: 

• Accuracy. The ADA'S positional and orientation accuracies are the 
same as the FA requirements. 

• Frequency and timeliness. Three SCPs per Patriot battalion for 
area defense and two SCPs per Patriot battalion for forward-area 
defense must be established. The number of SCPs and the timeliness 
is dependent on the battlefield and the mission. 

• Distribution. This control information should be distributed to the 
highest echelon SPCE and the Patriot-battalion S3. 



9-2 Artillery Surveys 



FM 3-34.331 



SURVEY PLANNING 



9-6. The maneuver commander initiates the requirement for survey planning 
(reference FM 6-2) by issuing guidance to the fire-support (FS) coordinator 
(FSCOORD). This guidance states the scheme of maneuver, the rate of 
movement, the anticipated enemy threat, and the critical phases of the battle. 

ARTILLERY COMMANDER OR FSCOORD 

9-7. The FSCOORD analyzes the commander's guidance to determine the 
need for passing of target information, for having first-round f i re-for-effect 
accuracy, and for massing of fires. The FSCOORD weighs the analysis against 
the ability to adjust fires, complete registration missions, and engage targets 
from new position areas. This begins the concept for a survey plan to provide 
common survey control. 

9-8. The FSCOORD must extract from the maneuver commander's guidance 
all information that allows visualization of the survey requirements for FS 
assets. The FSCOORD can gain most of the information by reviewing the 
scheme of maneuver, therateof movement, theeffects required on high-payoff 
targets, and the accuracy requirements for TA sensors. He must also 
determine whether it is more important to have survey support at the guns or 
at theTA assets first. 

9-9. Each artillery commander is responsible for establishing common control 
throughout his AO. The FSCOORD must disseminate to the appropriate 
artillery battalion HQ the established accuracy requirements in survey terms. 
Additional requirements or guidance derived by the FSCOORD must also be 
communicated. This should be done through face-to-face coordination or 
through the S3. The survey officer must be included in this coordination and 
should advise the FSCOORD and/or the S3 on the current survey capabilities 
and limitations. 

CORPS'S ARTILLERY SURVEY-PLANNING AND COORDINATING OFFICER 

9-10. The corps's artillery survey-planning and coordinating officer (SPCO) is 
responsible for the following: 

• Knowing the survey requirements and capabilities of all corps units 
(Figure 9-1, page 9-4). 

• Coordinating with the corps's Assistant Chief of Staff, G2 
(I ntelligence) (G2) to get intelligence estimates of the proposed work 
areas. These work areas should include— 

Enemy activity. 
Friendly forces. 
Other optional constraints. 

• Coordinating with the corps's G3 to get the following information for 
planning and coordinating intelligence and electronic-warfare (IEW) 
systems that require survey support (Figure9-2, page9-5, shows a 
corps survey-plan overlay). 

Positions of thecorps's artillery units (current and planned). 
Unit-movement plans. 



Artillery Surveys 9-3 



FM 3-34.331 



Corps 
artillery 



TAB 



as 



appropriate) v 



1 AN/TPQ-37 h 

i ii 

L, J | 



(as appropriate) 



i± 



FA 

bn 



DIVARTY 



Comm 



Topo 
survey 



FA bde -i 



*C 2 



t 



AN/TPS-25A i i AN/TPQ-36 * - 

ii i i- -, 

JL-r J I I 

L T ' I 



GS 
FAbn 



MLRSbn 



GSR FA bde 



w5 



FA 

btry 



T 



(as needed) 



NBC 



IEW 



i i 
i i 



7J7_ 

MET 



77TT: 

Mortars 






Engr 



Coordination only comm_ . 

Survey control (third order) 3_ 

Survey control (fourth order) 4 

Survey control (fifth order) 5 

Command and control C 2 



Figure 9-1. Survey Requirements and Capabilities of Corps Units 

Dates and times of movement. 
Priority of unit movement. 

• Making contact with the engineer topographic battalion's survey 
section and obtaining necessary details from the commander (for 
example, the attached platoon, the location of company SPCE, and the 
POCs). The engineer topographic battalions' survey section supports 
the FA and the ADA with third-order horizontal and vertical control 
points and azimuth marks for the division through the EAC and 
separate artillery brigades on a 24-hour basis. A topographic survey 
augments an FA survey with the information required for the 
following: 

EAC (two SCPs per Patriot battalion). 

Corps area (eight SCPs each 24-hour period and one SCP per 
DIVARTY or separate brigade each 24-hour period). 
PADS (starting and closing SCPs are provided at a maximum 
interval of 25 kilometers). 



9-4 Artillery Surveys 



FM 3-34.331 



FEBA 



FEBA 



^^^^f 



/'^fe^ 7 



)\ " — ' xx 




m 



/ 



/ 






/ 



\ / 



®^r.==— L = _. 



w 



XX 



^ 



CSD 



w 






x 

X 



^~ 






\N 



w % 



\\ 



% 



// 



'/ 



// 



'/ 






<X>— 



XXX 



LEGEND: 

= z zz z = Topographic survey 

DIVARTY or TAB survey 

£$. High-order SCP (established or 

/w\ preexisting) 

SCP established by topographic 
survey 

Ground-surveillance radar 



*W 



\(M/ Artillery-locating radar 
\g/ Air-defense radar 
\ a/ Direction-finding site 
ew/ Electronic warfare 
FA bn area 



Figure 9-2. Corps Survey-Plan Overlay 



Artillery Surveys 9-5 



FM 3-34.331 



MLRS (starting and closing SCPs are provided at a maximum 

interval of 30 kilometers). 
Making necessary arrangements with the corps's HQ and HQ 
company (HHC) for administrative and logistical support of the 
topographic survey platoon. 

Arranging and coordinating with the corps's aviation company for 
support if requested by the survey-section leader of the engineer 
topographic company. 

Maintaining a close working relationship with the topographic- 
survey-platoon leader, the corps's artillery units' survey officers, and 
the DIVARTY survey officers. This coordination ensures a timely 
three-way flow of information concerning survey operations and data 
collection. It also enhances the timely completion of the survey 
mission. 



9-6 Artillery Surveys 



Chapter 10 

Airfield-Obstruction and NAVAID Surveys 

This chapter acquaints Army surveyors with the terminology and the 
requirements for airfield-obstruction and NAVAID surveys. The content is 
general in nature due to the vast differences in airfield instrumentation, 
customer requirements, and FAA regulations. 

AIRPORT OBSTRUCTION CHARTS AND NAVAID SURVEYS 

10-1. AOCs and NAVAID surveys are extensive field or photogrammetric 
operations that are required by agreement between the FAA and theUSAASA 
and are specified in AR 95-2. Airfield-obstruction and NAVAI D surveying 
operations involve obtaining accurate and complete NAVAID and associated 
airport/heliport-obstruction and geodetic-positioning data. A precise 
geographic position of these navigational facilities is required to support the 
FAA and a wide range of NAS activities. AOC surveys provide source 
information on— 

Runways and stopways. 

NAVAI Ds. 

FAR-77 obstructions. 

Aircraft-movement aprons. 

Prominent airport buildings. 

Selected roads and other traverse ways. 

Cultural and natural features of landmark value. 

Miscellaneous and special-request items. 

10-2. AOC surveys also establish or verify geodetic control in the airport 
vicinity that is accurately connected to the NSRS. This control and the NSRS 
connection ensure accurate relativity between these points on the airport and 
other surveyed points in the NAS, including GPS navigational satellites. AOC 
data is used to— 

Develop instrument-approach and -departure procedures. 

Determine maximum takeoff weights. 

Certify airports for certain types of operations. 

Update official aeronautical publications. 

Provide geodetic control for engineering projects related to runway/ 

taxiway construction, NAVAID positioning, obstruction clearing, and 

other airport improvements. 

Assist in airport planning and land-use studies. 

Support activities such as aircraft-accident investigations and special 

projects. 



Airfield-Obstruction and NAVAID Surveys 10-1 



FM 3-34.331 



FAAAND FAR STANDARDS 



RUNWAYS 



NAVAIDS 



10-3. FAA Publication 405 (FAA 405) and FAR-77 outline the requirements 
for AOC surveys. Various areas, surfaces, reference points, dimensions, and 
specifications used in airfield surveys are described below. 



10-4. All length and width measurements are determined to the nearest foot. 
If the runway's threshold is displaced, the distance (in feet) is given from the 
beginning of the runway's surface. Determine the coordinates (latitude and 
longitude) of the runway's threshold and stop end at the runway's centerline. 
Elevations at the runway's threshold, stop end, and highest elevation (within 
the first 3,000 feet of each runway touchdown zone elevation [TDZE]) should 
be determined to the nearest 0.1 foot from the MSL. In addition, prepare 
runway profiles that show the elevations listed above, the runway's high and 
low points, grade changes, and gradients. Determine the elevation of a point 
on the instrumented runway's centerline nearest to the instrument landing 
system (ILS) and the glide-path transmitter to the nearest 0.1-foot MSL. 



10-5. Airports requiring airfield-obstruction and NAVAID surveys are 
instrumented runways. The exact point on the radar, the reflectors, the 
runway intercepts, and the ILS and microwave-landing-system (MLS) 
components depend on the survey type, the location, and the required 
accuracy. The requirement to verify the existing I LS/M LS, their proper 
description, and all components on or near the runway is mandatory. Obtain 
information for locating and describing all airfield features with help from 
airfield-operation, maintenance-section, and control-tower personnel. The 
following NAVAIDs are located on airports: 

• ILS. 

• MLS. 

• Precision approach radar (PAR). 

• Airport surveillance radar (ASR). 

10-6. The following NAVAIDs are not located on airports: 

• Tactical air navigation (TACAN). 

• VHF omnidirectional range (VOR). 

• Nondirectional beacon (NDB). 

• VOR and TACAN (VORTAC). 



OBSTRUCTIONS 



10-7. An obstruction is an object or feature protruding through or above any 
navigational imaginary surface that poses a threat to the safe operation of 
aircraft. Navigational imaginary surfaces or obstruction identification 
surfaces (01 Ss) are defined in FAR-77. I n the following paragraphs are some 
definitions, along with some samples. 



10-2 Airfield-Obstruction and NAVAID Engineering Surveys 



FM 3-34.331 



FAR-77, Section 77.28, Military-Airport Imaginary Surfaces (Figure 10-1 and 
Figure 10-2, page 10-4) 




LEGEND: 

A Primary surface 

B Clear-zone surface 

C Approach/departure-clearance surface (glide angle) 

D Approach/departure-clearance surface (horizontal) 

E Inner horizontal surface 

F Conical surface 

G Outer horizontal surface 

H Transitional surface 



Figure 10-1. General Plan View of an OIS 

10-8. Related to airport reference points (ARPs). These surfaces apply to 
all military airports. For the purpose of this section, a military airport is any 
airport operated by an armed force of the US. 

• Inner horizontal surface. An oval plane that is at a height of 
150 feet above the established airfield elevation. The plane is 
constructed by scribing an arc with a radius of 7,500 feet from the 



Airfield-Obstruction and NAVAID Engineering Surveys 10-3 



FM 3-34.331 













x5o>i 






y .^ y H 


* !^L 




^' ** ~+ \ 




Hj 


c> <- \ 


\^""^ F 


-S^^ 


"^v-** \ 


\^e y 


-•"^O^ 




^ k \m- _J^ 


<sy\ i 






^ E ) F 


G 


^^^ 






LEGEND: 


^^K. 




A Primary surface 






B Clear-zone surface 




^X / 


C Approach/departure-clearance surface 




(glide angle) (50:1) 




\ / 


D Approach/departure-clearance surface 




x / 


(horizontal) 




x / 


E Inner horizontal surface 




\ / 


F Conical surface (20:1) 






G Outer horizontal surface 






H Transitional surface (7:1) 




■* 



Figure 10-2. Partial Plan View of an OIS 

centerline at the end of each runway and interconnecting these arcs 
with tangents. 

• Conical surface. A surface extending from the periphery of the inner 
horizontal surface outward and upward at a slope of 20:1 for a 
horizontal distance of 7,000 feet to a height of 500 feet above the 
established airfield elevation. 

• Outer horizontal surface. A plane that is located 500 feet above the 
established airfield elevation, extending outward from the outer 
periphery of the conical surface for a horizontal distance of 
30,000 feet. 

10-9. Related to runways. These surfaces apply to all military airports. 

• Primary surface. A surface located on the ground or on water, 
longitudinally centered on each runway, and the same length as the 
runway. The width of the primary surface for runways is 2,000 feet. 
However, at established bases where substantial construction has 



10-4 Airfield-Obstruction and NAVAID Engineering Surveys 



FM 3-34.331 



taken place according to previous lateral-clearance criteria, the 2,000- 
foot width may be reduced to the former criteria. 

• Clear-zone surface. A surface located on the ground or on water at 
each end of the primary surface. The clear-zone surface is 1,000 feet 
long and is the same width as the primary surface. 

• Approach/departure-clearance surface. An inclined plane that is 
located symmetrical from the extended runway's centerline, beginning 
200 feet beyond each end of the primary surface at the centerline 
elevation of the runway's end and extending for 50,000 feet 
(Figure 10-3, page 10-6). The slope of the approach-clearance surface 
is 50:1 along the extended runway's centerline until it reaches an 
elevation of 500 feet above the established airport elevation. The 
surface then continues horizontally at this elevation to a point 
50,000 feet from the beginning point. The width of this surface at the 
runway's end is the same as the primary surface, then it flares 
uniformly and the width at 50,000 feet is 16,000 feet. 

• Transitional surfaces. These surfaces connect the primary surfaces, 
the first 200 feet of the clear-zone surfaces, and the approach/ 
departure-clearance surfaces to the inner horizontal surface, the 
conical surface, the outer horizontal surface, or other transitional 
surfaces. The slope of the transitional surface is 7:1 outward and 
upward at right angles to the runway's centerline. 

FAR-77, Section 77.29, Airport I maginary Surfaces for Heliports 

10-10. These surfaces apply to all military heliports. For the purpose of this 
section, a military heliport is any heliport operated by an armed force of the 
US. 

• Heliport's primary surface. The primary surface coincides in size 
and shape with the designated takeoff and landing area of a heliport. 
This surface is a horizontal plane at the elevation of the established 
heliport elevation. 

• Heliport's approach surface. The approach surface begins at each 
end of the heliport's primary surface, is the same width as the primary 
surface, and extends outward and upward for a horizontal distance of 
4,000 feet where its width is 500 feet. The slope of the approach 
surface is 8:1 for civil heliports and 10:1 for military heliports. 

• Heliport's transitional surfaces. These surfaces extend outward 
and upward from the lateral boundaries of the heliport's primary 
surface and from the approach surfaces at a slope of 2:1 for a 
horizontal distance of 250 feet from the centerline of the primary and 
approach surfaces. 

FAR-77, Section 77.5, Kinds of Objects Affected 

10-11. This section further defines an obstruction and applies to— 

• Any object of natural growth, the terrain, permanent or temporary 
construction or alterations (including equipment or materials used 
therein), and apparatus of a permanent or temporary character. 



Airfield-Obstruction and NAVAID Engineering Surveys 10-5 



FM 3-34.331 



500' elevation 




Ground 
surface 



Sq- 



25,000' 



200'- 



25,000' 



1,000' 



Longitudinal section 




Plan view 



LEGEND: 

A Primary surface 

B Clear-zone surface 

C Approach/departure-clearance surface (glide angle) 

D Approach/departure-clearance surface (horizontal) 

E Inner horizontal surface 

F Conical surface 

G Outer horizontal surface 

H Transitional surface 



Figure 10-3. Plan and Profile View of the Approach/Departure OIS 



10-6 Airfield-Obstruction and NAVAID Engineering Surveys 



FM 3-34.331 



Any permanent or temporary existing structure altered by a change in 
its height (including appurtenances) or lateral dimensions (including 
equipment or materials used therein). 



DATA 



10-12. TheARP location (in longitude and latitude) will be determined 
according to FAA 405. Field elevation is the highest point on any airport 
landing surface. 

AIRFIELD-DATA ACCURACY REQUIREMENTS 

10-13. All contiguous CON US-, Alaskan-, and Caribbean-area coordinates 
should be determined based on NAD 83 and/or WGS 84. Geodetic accuracy of 
orthometric heights are referenced to N AVD 88. The coordinates for the points 
on the airport require different degrees of accuracy. Tables 10-1 and 10-2 and 
Tables 10-3 through 10-5, pagelO-8, are examples of different accuracy 
standards for airfield data. FAA 405 contains the complete requirements. The 
horizontal accuracy requirements can be met through third-order, Class II 
traverse, GPS, or two-point intersection techniques. The vertical accuracy 
requirements dictate a minimum of third-order differential-leveling 
techniques. 

Table 10-1. Airport-Obstruction Accuracy Requirements 



Item 


Horizontal 
(ft) 


Orthometric 
(ft) 


Ellipsoidal 
(ft) 


Above Ground 
Level (ft) 


Non-man-made 
objects and man- 
made objects 
less than 200 feet 
above ground 
level that 
penetrate the 
OlSs. 


A primary surface. 


20 


3 


3 


NA 


Those areas of an approach 
surface within 10,200 feet of 
the runway's end. 


20 


3 


3 


NA 


Those areas of a primary 
transitional surface within 500 
feet of the primary surface. 


20 


3 


3 


NA 


Those areas of an approach/ 
departure surface that are 
both within 500 feet of the 
approach surface and within 
2,766 feet of the runway's end. 


20 


3 


3 


NA 



Table 10-2. Visual-NAVAID Accuracy Requirements 



Item 


Horizontal 
(ft) 


Orthometric 
(ft) 


Ellipsoidal 
(ft) 


Above Ground 
Level (ft) 


Airport beacon 


(1) 


NA 


NA 


NA 


Visual glide-slope indicators 


20 


NA 


NA 


NA 


Runway end identifier lights (REILs) 


20 


NA 


NA 


NA 


Approach lights 


20 


NA 


NA 


NA 


NOTE: The horizontal accuracy requirement for items coded "(1)" is 20 feet when located on a public- 
use airport or military airfield and 50 feet for all other locations. 



Airfield-Obstruction and NAVAID Engineering Surveys 10-7 



FM 3-34.331 



Table 10-3. Control-Station Accuracy Requirements 



Item 


Horizontal 
(cm) 


Orthometric 
(cm) 


Ellipsoidal 
(cm) 


Above Ground 
Level (cm) 


Primary airport control station (PACS) 1 


5 


25.0 


15 


NA 


Secondary airport control station (SACS) 2 


3 


5.0 


4 


NA 


Wide-Area Augmentation System (WAAS) 
reference station 1 


5 


10.0 


10 


NA 


WAAS reference station 3 


1 


0.2 


2 


NA 


Accuracies are relative to the nearest NGS-sanctioned continuously operating reference station. 
Accuracies are relative to the PACS and the SACS at the airport. 
Accuracies are relative to the other WAAS reference station at the site. 



Table 10-4. Electronic-NAVAID Accuracy Requirements 



Item 


Horizontal 
(ft) 


Orthometric 
(ft) 


Ellipsoidal 
(ft) 


Above Ground 
Level (ft) 


Air-route surveillance radar (ARSR) 


(1) 


100 


100 


NA 


ASR 


(1) 


10 


10 


NA 


DME: 
Frequency paired with localizer 
Frequency paired with MLS azimuth guidance 
Frequency paired with NDB 
Frequency paired with VOR 


1 

1 

(1) 
(1) 


1 
1 

NA 
NA 


1 
1 

NA 
NA 


NA 
NA 
NA 
NA 


NOTE: The horizontal accuracy requirement for items coded "(1)" is 20 feet when located on a public-use 
airport or military airfield and 50 feet for all other locations. 



Table 10-5. Airport-Runway Accuracy Requirements 



Item 


Horizontal 
(ft) 


Orthometric 
(ft) 


Ellipsoidal 
(ft) 


Above Ground Level 
(ft) 


Physical end 


1 


0.25 


0.2 


NA 


Displaced threshold (DT) 


1 


0.25 


0.2 


NA 


TDZE 


NA 


0.25 


0.2 


NA 


Supplemental profile points 


20 


0.25 


0.2 


NA 



REPORTING 



10-14. The required reporting for airfield surveys is not significantly different 
from that required for other survey operations. The parent unit will normally 
require all of the reports listed in Chapter 11 of this manual. I n addition to 
these routine reports, a special report (according to ARs 95-1 and 95-2, 
FAA 405, and FAR-77) will be required for the submission of the final data. 
For quick reference, the required documentation is listed below. 



10-8 Airfield-Obstruction and NAVAID Engineering Surveys 



FM 3-34.331 



AOC 



Airport Plan 



10-15. An AOC is a l:12,000-scale graphic depicting FAR-77 guidance. An 
AOC represents objects that penetrate airport imaginary surfaces, aircraft 
movement and apron areas, NAVAIDs, prominent airport buildings, and a 
selection of roads and other plani metric detail in the airport vicinity. Also 
included are tabulations of runway and other operational data. AOC data is 
current as of the date of the field survey. TheAOC consists of four sections: 

• Airport plan (AP). 

• Runway plans and profiles (RPP). 

• Tabulated operational data (TOD). 

• Notes and legends (NL). 

10-16. Each section (all contents and the general format) should conform to 
the sheet style (obstruction chart [OC] 000) represented in FAA 405. An AOC 
is published on E50 chart paper (or equivalent) with border dimensions of 30 x 
42 or 30 x 48 inches. The long dimension may be either in the north-south or 
east-west direction and should have a 3 /4-inch space between the border and 
the trim line. If the AP and the RPP will not fit on the front of the chart, the 
RPP is printed on the back. 



10-17. The depiction of the AP depends on the surface type and whether an 
obstruction survey was accomplished. A detailed explanation of what 
pertinent information to depict is included in FAA 405, Section 10.1.3. For 
example, an AP for a specially prepared hard surface (SPHS) runway will 
include the following information: 

Runway's length and width. 

DTs. 

The physical end of the runway. 

Airport elevation. 

TDZE. 

Magnetic bearing. 

Runway numbers. 

Obstructions. 

NAVAIDs. 

Meteorological apparatus. 

ARP. 

Runway Plans and Profiles 

10-18. A detailed explanation of what information to depict is included in 
FAA 405, Section 10.1.4. The RPP should include the foil owing: 

• Proper angular orientation. 

• A horizontal scale of 1:12,000 and a vertical scale of 1 inch equal to 
100 feet. 

• Adequate area of coverage of the primary and approach surfaces. 

• A plan view of the runway as shown on theAP. 

• A profile view of objects carried in the plan view. 

• A profile view of objects penetrating the approach surfaces. 



Airfield-Obstruction and NAVAID Engineering Surveys 10-9 



FM 3-34.331 



• The correct approach surface or precise-instrument-runway (PI R) 
surface. 

• The correct numbering scheme of objects in the profile. 

• A north arrow. 

NOTE: A PIR has an existing instrument-approach procedure that uses an ILS or a 
PAR. PI R also refers to a runway for which a precision approach system is planned 
and is so indicated by an FAA-approved airport layout plan, a military-airport layout 
plan, any other FAA planning document, or a military-airport planning document. 

Tabulated Operational Data 

10-19. The TOD should show the following: 

• The airport location point (ALP) listed in degrees and minutes. 

• TheARP listed in degrees, minutes, and three-decimal-place seconds. 

• A runway data table with runway numbers, appropriate latitude and 
longitude coordinates, andTDZEs. 

• Geodetic azimuth from the approach end to the stop end, reckoned 
from the north. 

• Additional information pertaining to runways with DTs. 

Notes and Legends 

10-20. A detailed explanation of what pertinent information to depict is 
included in FAA 405, Section 10.1.6. The NL should include the following: 

Horizontal datum. 

Vertical datum. 

Map projection. 

Airport elevation. 

A legend. 

Graphic horizontal and vertical scales. 



FORMS 



10-21. In addition totheAOC, each airfield report requires completion of the 
following forms: 

• DAForm5821-R. 

• DAForm5822-R. 

• DAForm5827-R. 

10-22. An airfield compilation report (DA Form 5821-R) (FigurelO-4) is a 
tabulation of all the information obtained from the survey. TablelO-6, 
pagelO-12, includes instructions for completing this form. 

10-23. PAR or ground-controlled-approach (GCA) data is entered on 
DA Form 5822-R. The completion of this form is self-explanatory (Figure 10-5, 
page 10-13). 

10-24. I LS data is entered on DA Form 5827-R (FigurelO-6, pagelO-14). The 
completion of this form is self-explanatory. 



10-10 Airfield-Obstruction and NAVAID Engineering Surveys 



FM 3-34.331 





Airfield Compilation Report 
Few una Ol Blla FQfHl, Mfl FM 3-34.3' 1. Eh* preparer: agoncy lsT^*DOC- 






Si^TVAaEHCv. 30th Engineer Battalion 


appo=t«*ve McCoy Army Airfield 


" CMY 




°" v Fort McCoy 


s>Te Wisconsin 


[GfflGM ^ 


3U"VI-'- i;i|h 
Oct 1986 


JUPFOU 

BEFf PENCE PO NT 


ARP 


•j- T_;E 

43°57'33.458"N 


LC«aT^DE 
90°44'14.641"W 


,1 7. C« £* *M*ti-E 

-01°34'15.6" 


AIRPQflT 
LDCVlO PONT 




uHTySE 


.^sJiT^QE 


DecLWATiDN 


*PFO*t =LEVA*-.Gn 
<nr*t*i 837.3 MSL 


LQCATB E0R 01 


C0N _3 CL rcWERTLOSH 

elev*tCh<hi*w1| 871.2 MSL 


DATUM WGS-84 


1. Flic S-p.*v 


MWQCTEUTA 


ElEVA'O- 


LATITUDE 


UOHHTUM 


vR-coce 


PEMAPK3 


OFFICE 
:JU.:i 


NDB (CMY) 


1,020.1 


43°56'16.1"N 


90°38'30.3"W 


86/01 






Windsock(l) 


860.4 


43°57'35.7"N 


90°43'58.5"W 


86/01 






Beacon (13) 


896.4 


43°57'14.5"N 


90°44'05.8"W 


86/01 






WDI 


845.8 


43°57'35.7"N 


90°43'58.1"W 


86/01 






Tetrahedron 


834.7 


43°57'36.1"N 


90°43'58.4"W 


86/01 






Control Tower (9) 


911.6 


43°57'22.5"N 


90°44'05.9"W 


86/01 






Maltese Cross #L 


830.5 


43°57'30.8"N 


90°43'59.7"W 


86/01 






Maltese Crosses 


829.8 


43°57'26.4"N 


90°44'15.9"W 


86/01 






Maltese Crosses 


832.9 


43°57'22.8"N 


90°43'51.6"W 


86/01 


































H-HWAV 


Q3P1-CD 

T-R 
UnGTH 


EJLEVArtSN 


WTIIUM 


UJhijrMPE 


WOTH 
LE»3> 


aEOZETIDAZ.HI 
MAO BF.ARhGlNl 


office 

COTE 


EOR29 
TDZE 


NA 


831.8 


43°57'27.478"N 


90°43'48.699"W 


100.00 
4,211.00 


292°09'26.2" 
290°58'26.2" 




EOR 11 


NA 


822.4 


43°57'43.164"N 


90°44'42.017"W 


4,211.00 


112°09'25.8" 
110°58'25.8" 




TDZE 
11/29 


NA 


829.5 


43°57'32.027"N 


90°44'03.899"W 


NA 


NA 




EOR 19 


NA 


824.7 


43°57'44.922"N 


90°44'08.802"W 


1 90.00' 
2,962.90 


195°25'26.5" 
194°14'26.5" 




EOR 01 


NA 


837.3 


43°57'16.715"N 


90°44'19.574"W 


90.00 
2,962.90 


15°25'27.3" 
14°14'27.3" 




EOR 01 
3T 


1,326.7 


835.7 


43°57'04.089"N 


90°44'24.408"W 


50.00 
1,326.70 


NA 






DA Form 5821 


-R, AUG 89 





Figure 10-4. Airfield Compilation Report 



Airfield-Obstruction and NAVAID Engineering Surveys 10-11 



FM 3-34.331 



Table 10-6. 


Instructions for Completion of DA Form 5821 -R 


Block Name 


Instruction 


Survey agency 


The agency conducting the field survey. 


Airport name 


The official airport name as determined by the FAA. 


Identifier 


The airport location-identifier designator as listed in FAA Publication 
7350.5-V. 


City 


Self-explanatory. 


State 


Self-explanatory. 


Edition 


The number of times the airfield has been surveyed by the agency 
listed in the survey-agency block. Identify the original survey as 1 and 
subsequent surveys as 2, 3, and so on. 


Survey date 


The year of declination. 


ARP 


The physical location of the ARP. 


ARP latitude 


Self-explanatory. 


ARP longitude 


Self-explanatory. 


Delta azimuth or 
theta angle 


The grid convergence for the ARP. 


ALP 


The physical location of the ALP. 


ALP latitude 


Self-explanatory. 


ALP longitude 


Self-explanatory. 


Declination 


The magnetic declination of the ARP. 


Airport elevation (ft) 


See the glossary. 


Located 


A short narrative description (include the latitude and the longitude). 


Control-tower floor 
elevation (ft) 


Self-explanatory. 


Airport data 


Object or airfield feature observed (use additional sheets as required). 


Elevation 


Self-explanatory. 


Airport-data latitude 


Self-explanatory. 


Airport-data longitude 


Self-explanatory. 


Year code 


The year and month surveyed (for example, April 87 is written 8704). 


Remarks 


Self-explanatory. 


Office code 


Leave blank (may be used by other offices). 


Runway 


The numerical designation of the runway. 


DT length 


See the glossary. 


Runway-end elevation 


Self-explanatory. 


Runway-end latitude 


Self-explanatory. 


Runway-end longitude 


Self-explanatory. 


Width/length 


The physical width and length of the runway's surface. 


Geodetic azimuth/ 
magnetic bearing 


Self-explanatory. 


Office code 


Leave blank. 



10-12 Airfield-Obstruction and NAVAID Engineering Surveys 



FM 3-34.331 



AIRPORT NAME 



Precision Approach Radar (GCA) Data 

For use of this form, see FM 3-34.331 ; the proponent agency is TRADOC. 



McCoy Arvwy AwfCeld/ 



CITY 



&r<McCoy 



STATE 



mow 



PAR COMPONENTS AND PERTINENT RUNWAY DATA 
Numbered items correspond to the diagram below. 



1 . PAR Antenna 



LATITUDE 



SURVEY DATE (Mo./Day/Year) 



LONGITUDE 



(1/100 Second) 



2. Touchdown Reflector 



3. The point on runway C/L closest to the 
Touchdown Reflector (Item 2). 



4. Runway C/L End. 



99 



5. Runway C/L End. 



6. The point on runway C/L closest to PAR Antenna. 




7. Displaced Threshold (If applicable). 



ELEVATION 



(1/10 Foot) 



(J PAR Antenna - Enter Numeral 1 In circle to Indicate PAR Antenna Position, 
s\ Touchdown Reflector - Enter Numeral 2 In circle to Indicate Touchdown Reflector. 



PAR - GROUND DISTANCE 



3to7 

(If applicable) 



FEET 



1 to 6 



FEET 



3 to 6 



FEET 



2 to 3 



FEET 



3 to 4 



FEET 



GEODETIC AZIMUTH SOUTH 
4t0 5 ° 



ADD APPLICABLE NUMBERS TO CIRCLES AND RUNWAY ENDS. SHOW NORTH ARROW. 



© 

© 





®-y —!-":#" 



© 



^-O 



\ 







o 



..... 



«£ 



© 



X7 



-© 



DA Form 5822-R, AUG 89 



Figure 10-5. PAR Data 



Airfield-Obstruction and NAVAID Engineering Surveys 10-13 



FM 3-34.331 



Instrument Landing System Data 

For use of this form, see FM 3-34.331 ; the proponent agency Is TRADQC. 



AIRPORT NAME 



McCoy Arvwy Airfield/ 



CITY. 



&r<McCoy 



STATE 



mow 



SURVEY DATE (Mo./Day/Year) 

@999 



ILS COMPONENTS AND PERTINENT RUNWAY DATA 
Numbered items correspond to the diagram below. 



LATITUDE 



LONGITUDE 



(1/100 Second) 



ELEVATION 



(1/10 Foot) 



1. Localizer Antenna (Course Array): Point on ground 
beneath the localizer antenna. 



2. Glide Slope Indicator (GSI): Center of the base 
supporting the antenna. 



3. The point on runway C/L closest to the base of the 
Glide Slope Indicator Antenna (Item 2), 



5 



4. Runway C/L End. 



5. Runway C/L End. 



4& 



9 '3 



6. The point on runway C/L closest to the base of 
the offset Localizer (Case 2). 



z 



s: 



MARKERS 



LATITUDE 



LONGITUDE 



(1 / 10 Second) 



GROUND DISTANCE 

TO 

END OF RUNWAY 



INNER OR B. C. MARKER (RUNWAY END) 



feet 



MIDDLE MARKER (RUNWAY END) 



feet 



OUTER MARKER (RUNWAY END) 



feet 



LOCALIZER - GROUND DISTANCE 



Case 1 (normal) 



Case 2 (offset) 



1 to 5 



FEET 



1 to 6 



FEET 



2 to 3 



FEET 



5 to 6 



FEET 



3 to 4 



FEET 



GEODETIC AZIMUTH SOUTH 
O ' " 

4 to 5 



ADD APPLICABLE NUMBERS TO CIRCLES AND RUNWAY ENDS. SHOW NORTH ARROW. 

Case 1 C~") Case 2 




O 




® 



?-o 



\ 



n~ 



90°\ 



O 



Case 2 



--I-- o. 



$/ \ 



© 



A-O 



DA Form 5827-R, AUG 89 



Figure 10-6. ILS Data 



10-14 Airfield-Obstruction and NAVAID Engineering Surveys 



Chapter 11 

Reports, Briefings, and Operation Orders 

All survey and survey-support activities must be documented. 
Additionally, unit commanders or visiting dignitaries have to be informed 
about the status of the project. The most common means of accomplishing 
these two tasks are reports and briefings. This chapter gives general 
guidance and recommended formats for these reports and briefings and for 
operation orders (OPORDs). This information is not intended to replace 
unit SOPs or official correspondence-preparation guidance but rather to 
supplement them and provide for a standardized procedure and format. 
Section III of this chapter includes a sample survey SOP and supporting 
annexes. 



SECTION I - REPORTS 



11-1. All reports should be treated as for official use only (FOUO) and 
safeguarded accordingly. In many instances, reports will be classified and 
appropriate safeguard measures are mandatory. All activities and events of a 
survey should be documented in a report. Reports can take many forms, and 
their primary uses are to— 

• Provide documentation of the project. 

• Serve as a historical record of accomplishment on problems. 

• I nform commanders of project status. 

• Provide information and data to planners and users. 



GENERAL 



11-2. All reports may not address each subject, but they will serve at least one 
of the above functions. A well-planned survey project can be broken down into 
phases. Each phase will require at least one report. These phases include— 

• Initial site visitation. 

• Field recon. 

• Project execution. 

• Compilation and computing. 

11-3. In some situations, it may be convenient and practical to combine one or 
more of these phases and to prepare a consolidated report. Reports are 
prepared to provide information and should not be written just to fulfill a 
requirement. 



Reports, Briefings, and Operation Orders 11-1 



FM 3-34.331 



I SVT REPORT 



11-4. The initial site visitation is usually a preliminary visit that is used to 
gather general information. The information collected is generally used for 
logistical purposes. This does not mean that technical information is not 
gathered, but gathering information is not necessarily the primary function of 
the visit. The initial site visitation will normally be conducted by the survey- 
section leader and the project's noncommissioned officer (NCO). Depending on 
the nature of the project, the survey-platoon leader may also be included. I n 
all cases, an I SVT report is required. A battalion or company SOP will usually 
designate the individual responsible for completing the report as well as the 
exact format to be used. Annex A of the sample survey SOP shows the format 
for an I SVT report. Any information that could be used at a later date should 
be included. 

11-5. The report should be broken down into readily identifiable numbered 
and titled paragraphs as follows: 

Paragraph 1. References. The project directive or technical OPORD 
(TECHOPORD) number. 

Paragraph 2. Personnel. The name, rank, and telephone number of all 
personnel involved in the recon. 

Paragraph 3. Key Personnel Contacts. The name, rank or position title, 
address, and telephone number of all key individuals contacted while 
conducting the visit. This paragraph is often combined with paragraph 2. 

Paragraph 4. Objective. The objective of the I SVT. 

Paragraph 5. Discussion. A discussion of exactly what occurred and what 
conversations took place (include only the most extensive). This paragraph 
will contain subparagraphs concerning logistical and technical information. 
All arrangements for lodging, food, medical, and other support must be listed 
and should include specific details. Any technical information should belisted; 
however, if extensive technical details are available, it may be advisable to 
include them in an appendix to the basic report. The key to the discussion 
paragraph is to list all information that is available. The report may be the 
only source of information for later activities on the project. 

Paragraph 6. Recommendations. The specific recommendations for the 
conduct of the next phase of the project. These recommendations should 
include the number of personnel, the start date, and the tasks to be 
accomplished. 

Paragraph 7. Funding. The fund citation. It may also specify the funds 
expended on the I SVT and any information concerning funding of the next 
phase of the project. 

Paragraph 8. Work Hours. The total number of work hours broken down by 
rank. This information can be used for projecting the time required on similar 
future projects. 

Paragraph 9. Equipment. The type of vehicles; the vehicles' identification 
numbers; the miles driven; and petroleum, oils, and lubricants (POL) 
information. 



11-2 Reports, Briefings, and Operation Orders 



FM 3-34.331 



11-6. The report must always be signed. A standard military signature block 
should be used. Any required appendix(es) should be attached. A copy of the 
report should be included with the project folder and the original forwarded to 
the appropriate commander. 



RECON REPORT 



NARRATIVE 



11-7. Therecon report will typically be longer than the I SVT report. It should 
contain logistical and technical information. The recon report is broken down 
into three major sections— narrative, graphic, and control cards. 



11-8. The narrative section is somewhat similar to the I SVT report. It 
contains much of the same type of information; however, it will be greatly 
expanded. Any information that could be used at a later date should be 
included. The report should be broken down into readily identifiable 
numbered and titled paragraphs (some of the subparagraphs may be deleted if 
they serve no purpose) as follows: 

Paragraph 1. References. The project directive or order number. The I SVT 
report should be listed if available. 

Paragraph 2. Personnel. The name, rank or position title, unit, and 
telephone number (both home station and remote site) of all personnel 
involved in the recon. 

Paragraph 3. Key Personnel Contacts. The name, rank or position title, 
address, and telephone number of all personnel, offices, or agencies that were 
contacted during the recon (include military message addresses). This 
paragraph is extremely important for rights of way and access to private 
lands. Agreements made with landowners and/or property custodians should 
be listed, and a written permission document should be prepared and signed 
and a copy included as the last annex of the I SVT report. 

Paragraph 4. Objective. The objective of therecon. It should be very specific 
and should include the nature of the recon (for example, triangulation, 
traverse, level, or plane table). 

Paragraph 5. Discussion. A discussion of the project. This paragraph will 
typically be the longest and will normally be broken down into subparagraphs. 
All details must be listed and specified. The following subparagraphs should 
be included: 

• Administrative, legal, and logistical support. A complete listing 
of all the support that has been arranged for the project. The list 
should include the foil owing information: 

Medical facilities. Identify the nearest military medical facility 
for routine medical problems and the nearest emergency medical 
facility. 

Lodging and mess facilities. List the arrangements, location, 
and condition of the facilities if the military installation can 
provide lodging and messing. Indicate whether or not the use of 
the mess facilities will detract from the execution of the project. 



Reports, Briefings, and Operation Orders 11-3 



FM 3-34.331 



Contracts. Include copies of all legal contracts that authorize the 
surveyors' entrance onto private and other nonfederal land. 
Identify the POC at the J AG that coordinated or generated the 
documents in case future complications or disagreements occur. 

Controlled areas. List the requirements to be followed if the 
surveyors must enter secure or sensitive areas (classified 
equipment or systems). Provide the customer's security officer 
with the names and security classifications of the surveyors before 
starti ng the project. I f the surveyors must be escorted, identify the 
primary escort and whether the surveyors can go into the 
controlled area at anytime. Identify how access to the controlled 
areas will affect the scheme of extending survey control. 

Morale factors. List all arrangements that have been made for 
mail delivery, pay processing, and financial assistance. 

Other logistic information. List any additional support 
information that is required. MOAsfor POL and other expendable 
supplies and vehicle-maintenance support should be included as 
annexes. Include coordination procedures for any secured area (for 
example, a fenced in area that is locked after duty hours). 

• Environmental factors. Any environmental factors that could affect 
the project. These may include, but are not limited to, the following: 

Weather. The expected weather conditions, to include long-range 
forecasts and normal weather patterns for the project area. 

Terrain. The type of terrain to be expected and how it will affect 
access to existing and proposed SCPs. How landforms will affect 
intervisibility and the proposed survey scheme. 

Flora and fauna. The types of plants and animals that inhabit 
the area. Particular attention should be given to poisonous plants 
and dangerous animals. 

Dangerous areas/restricted zones. A brief description of the 
type and location of any dangerous areas or restricted zones. 
Annotate them on the overlay. 

• Technical information. A listing of all work that was accomplished 
(for example, recovery, check angles, and check distances). It should 
also contain- 
All proposed starting and ending stations and their conditions. 
Line of sight information (also included in the graphic section). 
The accuracy of the figures (if applicable). 

Any other information of a technical nature that the field-survey 
party may need to know. 

• Source materials. A complete list of all source materials (such as 
trig lists, data cards, map sheets, and overlays) and the agency or 
office of origin. A copy of these materials should be attached behind 
the station description cards. 

Paragraph 6. Recommendations. Any recommendations (this paragraph 
will be lengthy and should be very detailed). It should include 



11-4 Reports, Briefings, and Operation Orders 



FM 3-34.331 



GRAPHIC 



recommendations that are based on sound technical principles that are within 
the capabilities of the unit. Include detailed information about the following: 

Methods of survey. The exact methods, procedures, and accuracy 
requirements. 

• J ob estimates. The estimated amount of personnel and time. Using 
this information, a cost estimate should be prepared and contained 
within this paragraph. If it is lengthy, include supporting data sheets 
as an annex. 

• Equipment. The equipment required todothejob. This will normally 
beTOE-authorized equipment; however, in some cases, it may be 
necessary to obtain other equipment (for example, chain saws). 
Indicate how and where the equipment will be obtained (for example, 
a cement mixer from the Directorate of Public Works (DPW), Roads 
and Grounds Division). 

• Time schedule. The project's time schedule (if the start date is 
known). For lengthy projects that must be broken down into phases, a 
milestone schedule should be developed and enclosed as an annex. 

Paragraph 7. Funding. Funds expended during the recon. Also include 
information such as the fund citation and source. 

Paragraph 8. Work Hours. The work hours expended (broken down by rank 
and activity performed [for example, POC meetings, POL and maintenance 
support, administrative requirements, and field recon]). This information will 
be helpful for planning and estimating similar future projects. 

Paragraph 9. Equipment. A list of all the equipment used to conduct the 
recon. Include the types of vehicles, the vehicles' identification numbers, the 
miles driven, POL data, and any other equipment actually used by the recon 
party. 



11-9. This section will usually take the form of overlays and/or maps. Use 
standard topographic and military symbols (as listed in FMs 21-31 and 
101-5-1) when annotating overlays and maps. At a minimum, an overlay 
should contain the following information: 

• Known, usablesurvey control stations (horizontal and vertical). 

• Proposed survey stations. 

• Dangerous areas and restricted zones. Show on the overlay and on all 
available maps. 

• Other information that will assist the survey project. I nclude possible 
intersection stations that will be visible from several main-scheme 
stations. 



CONTROL CARDS 



11-10. This section should be a compilation of DA Forms 1958 and 1959 that 
were completed during the recon. The control cards must be complete, 
accurate, formatted correctly, and of high enough quality to permit them to be 
reproduced with minimal expenditure of time and labor. 



Reports, Briefings, and Operation Orders 11-5 



FM 3-34.331 



PROGRESS REPORT 



VERBAL 



WRITTEN 



11-11. Progress reports are generally less formal than the other types of 
reports but are just as important. They are designed to keep the commander 
informed of progress. The time interval for progress reports will be 
established by the commander and included in the project directive. Normally, 
progress reports will be submitted weekly and, in some cases, daily verbal 
reports may be required. Progress reports may not be required for small 
projects. 



11-12. A verbal report follows the same identical format as a written progress 
report. The sender and the receiver should have a copy of the premade format 
to follow. Only those lines that are applicable are filled in. The field copy is 
included in the project file for use in compiling a written weekly or end-of- 
project report. 



11-13. A written progress report normally includes a cover form and a data 
sheet. The data sheet is a fill-in-the-blank form. Those areas not applicable 
are left blank. All information must be as accurate as possible. The tendency 
to hold back production levels cannot be tolerated. Annex D of the sample 
survey SOP is a recommended guide for determining progress. A copy of this 
report is forwarded to the parent unit and a copy is included in the project file. 
These reports are essential for the compilation of the final project report. 



END-OF-PROJ ECT REPORT 



11-14. An end-of-project report is used to inform the commander and the 
customer that the project has been completed. The results of the project will 
generally be listed on DA Form 1962. Copies of DA Form 1959, map overlays, 
and other graphics may be included. Annex E of the sample survey SOP shows 
theformat for an end-of-project report. The report should be broken down into 
readily identifiable numbered and titled paragraphs, as follows: 

Paragraph 1. References. A complete listing of all orders, letters, project 
directives, and memorandums for record (MFRs) concerning the project. 
Normally, the other reports will not be listed as references. 

Paragraph 2. Personnel. The name and rank of all personnel participating 
in the project. The inclusive dates of their involvement should also be listed. 
This paragraph can be further broken down as follows: 

• F ield-crew personnel from the parent unit. 

• Visiting or inspecting personnel (the unit or office should also be 
included). 

• Local officials directly involved in the project. 

Paragraph 3. Objective. The specific mission statement. 

Paragraph 4. Discussion. A detailed discussion of exactly what transpired 
during the conduct of the project. Specific dates and details should be 



11-6 Reports, Briefings, and Operation Orders 



FM 3-34.331 



included. The milestone objectives outlined in the recon report should be 
discussed. I ndicate whether the project was kept on schedule, or fully explain 
the reasons for falling behind schedule. 

Paragraph 5. Problem Areas. Specific problem areas and the solutions to 
the problems. This information becomes a historical record to be used for 
future planning purposes. Technical information will be included in the 
narrative and graphic sections of the recon report. 

Paragraph 6. Funding. All fund citations and a total of all funds expended. 
The I SVT and recon reports are the sources for this information. Copies of all 
travel vouchers and other expenses should be included. 

Paragraph 7. Work Hours. The total number of expended work hours 
(broken down by rank). A composite of all progress reports should be included. 

Paragraph 8. Conclusions and Recommendations. Specific conclusions 
and recommendations. 



INCIDENT REPORT 



VERBAL 



WRITTEN 



11-15. An incident report should be submitted any time there is an unusual 
occurrence that could have an impact on the project. I ncidents such as 
vehicular accidents, equipment damage, and personnel injuries must be 
reported. There is no set format for an incident report. The initial report can 
be verbal or written. 



11-16. The parent unit should be notified as soon as possible after the 
incident. This should be accomplished using a telephone, a radio, or an 
electronic message. The verbal report may be fragmentary because all the 
information may not be available or verified. The notification should answer 
the following questions: 

• Who? Who was involved. 

• What? What happened and what is being done to correct the incident. 

• When? What time and date did the incident happen. 

• Where? Where did the incident happen. 



11-17. In all cases, a written report is prepared and forwarded to the parent 
unit with copies going to the local POC (if appropriate) and in the project file. 
The written report will address the same questions as the verbal notification, 
but the significant difference will be the amount of detail. The written report 
should contain all details concerning the incident and must include written 
statements from any or all witnesses to the incident. I n the case of accidents 
or equipment damage, preventive measures to preclude recurrence should be 
included. A copy of the written report should be included in the project file 
and, if significant, the incident should be listed within the problem areas of 
theend-of-project report. 



Reports, Briefings, and Operation Orders 11-7 



FM 3-34.331 



REPORT DISPOSITION 



11-18. The reports should be submitted through the project's operations 
officer for technical evaluation and completion. The reports are then 
forwarded to the company commander and the battalion S3 for information or 
approval. Copies of the reports should be kept in the project files for 
documentation (audit trail) and historical purposes. 



SECTION II - BRIEFINGS 



11-19. In addition to reports, briefings are used to update commanders and 
other key visitors on the project's status. There are two general briefing 
categories— impromptu and deliberate. 



IMPROMPTU BRIEFING 



11-20. The impromptu briefing is the simplest and yet the most difficult type 
of briefing. It is simple because it requires a minimum of support facilities and 
materials; however, it is also difficult because a thorough knowledge of all 
aspects of the project is absolutely essential, but the preparation time is 
usually very short. The scenario for an impromptu briefing is very simple. The 
commander or other visiting official arrives for a site visitation and requests 
an update. The 01 C, theNCOIC, or another designated individual is expected 
to bring this person up to date on the project's status. The project progress 
reports are an invaluable source of information. Additionally, up-to-date maps 
of the project should be kept solely for the purpose of briefings. Other charts 
and statistical data that can be updated quickly are also advisable. The 
success of the briefing will depend primarily on the professionalism and 
knowledge of the briefer. The importance of the briefing cannot be 
overemphasized. An impressive impromptu briefing earns respect of those 
being briefed and builds their confidence that thesurvey team can accomplish 
its missions. 



DELIBERATE BRIEFING 



11-21. There are several types of deliberate briefings. They include 
information, decision, mission, and staff briefings. 



INFORMATION BRIEFING 



11-22. An information briefing is designed to inform the listener. The 
information briefing deals primarily with facts. It includes a brief introduction 
to define the subject and to orient the listener. It does not include conclusions 
or recommendations. Examples of when an information briefing might be 
appropriate are— 

• High-priority information that requires immediate attention. 

• Complex information (such as complicated plans, systems, statistics, 
or charts) that requires a detailed explanation. 

• Controversial information that requires elaboration and explanation. 



11-8 Reports, Briefings, and Operation Orders 



FM 3-34.331 



DECISION BRIEFING 



11-23. A decision briefing is designed to obtain a decision (or an answer to a 
problem). In the higher HQ, the decision briefing is used for most matters 
requiring command decisions, including tactical matters. In the division HQ 
and below, a more informal type of the decision briefing is used. At the outset, 
the briefer must state that the object of the briefing is to secure a decision. At 
the conclusion, if no decision has been given, the briefer must ask for one. The 
briefer should be certain of understanding the decision thoroughly. If 
uncertain, the briefer must ask for clarification. The decision briefing may be 
compared to an oral staff study, in that it contains each of the major elements 
of a staff study. The following steps are the most logical sequence of events for 
a decision briefing: 

Step 1. Isolate, define, and state the issue. Explain that the purpose of the 

briefing is to secure a decision. Include background information to show what 

led to the situation and why a decision is necessary. 

Step 2. State any assumptions. Assumptions must be both reasonable and 

supportable. 

Step3. Present thefacts bearing on the situation. This portion of the briefing 

is essentially the same as that for an information briefing, and the same rules 

generally apply to both types of briefings. All the important facts should be 

stated objectively, accurately, and fully. Facts that have a direct bearing on the 

problem and are already known to the person being briefed should be 

reviewed. Since this briefing should result in a decision, the listener is 

reminded of all the pertinent facts directly related to the problem. New facts, 

which are unknown to the person being briefed, should be limited to those 

that have a direct bearing on, or might influence, the decision. 

Step 4. Discuss possible courses of action. The courses of action are stated 

and briefly analyzed. The advantages and disadvantages of each course are 

pointed out and compared in the discussion paragraph of the staff study. 

I ndicate possible results of each course of action and any potential dangers 

involved. 

Step 5. State the conclusion. State the degree of acceptance or the order of 

merit of each course of action. 

Step 6. Make a recommendation. State the recommendation so that it may be 

used as a decision on the commander's approval. On presenting the 

recommendation, be prepared to discuss the coordination involved. Following 

the briefing, if the chief of staff is not present, inform the staff secretary, 

executive officer, or other appropriate administrative assistant of the 

commander's decision. 



MISSION BRIEFING 



11-24. A mission briefing is used under operational conditions to impart 
information, to give specific instructions, or to instill an appreciation of a 
mission. I n an operational situation or when the mission is of a critical nature, 
it may become necessary to provide individuals or smaller units with more 
data than was provided in the orders. A mission briefing reinforces orders, 
provides more requirements and instructions for the individuals, and provides 
an explanation of the significance of their role. This type of briefing is 



Reports, Briefings, and Operation Orders 11-9 



FM 3-34.331 



presented with care to ensure that it does not cause confusion or conflict with 
orders. Depending on the nature of the mission or the level of the HQ, a 
mission briefing is usually conducted by one officer, who may be the 
commander, an assistant, a staff officer, or a special representative. 



STAFF BRIEFING 



Attendance 



Scheduling 



Topics 



Procedures 



Staff Estimates 



11-25. A staff briefing is used to secure a coordinated or unified effort. This 
may involve the exchange of information, the announcement of decisions 
within a command, the issuance of directives, or the presentation of guidance. 
To accomplish these results, a staff briefing may include characteristics of an 
information, a decision, a mission, or any combination of these briefings. 



11-26. Attendance at a staff briefing varies with the size of the HQ, the type 
of operation being conducted, and the personal desires of the commander. 
Generally, the commander, the deputy or executive officer, the chief of staff, 
the administrative assistant, and the senior representative of each 
coordinating- and sped a I -staff section will attend. Representatives from major 
subordinate commands may also be present. 



11-27. I n garrison, staff briefings are normally scheduled periodically. 
U nscheduled staff briefings are called as the need arises. I n HQ of larger 
units, staff briefings are often held on a regularly scheduled basis. I n combat, 
staff briefings are held when required by the situation; however, at corps and 
higher levels, staff briefings normally are regularly scheduled events. Staff 
briefings are valuable in operational situations because full appreciation of 
the situation by the commander and staff is difficult to achieve by other 
means. 



11-28. Matters discussed at staff briefings will vary. At lower levels, topics of 
immediate concern to the unit and its operations are discussed, while at 
higher levels the briefing may deal more with matters of policy. I n field or 
combat operations, tactical matters will predominate. When staff briefings are 
held on a regularly scheduled basis, the substance of each staff officer's 
presentation may be for updating material previously presented. 



11-29. The chief of staff usually presides over the staff briefing, calling staff 
representatives to present matters that interest those present or that require 
coordinated staff action. Each staff officer must be prepared to brief on their 
area of responsibility. 



11-30. The presentation of staff estimates culminating in a commander's 
decision to adopt a specific course of action is a form of staff briefing used in 



11-10 Reports, Briefings, and Operation Orders 



FM 3-34.331 



the combat HQ. Staff officers involved in this type of briefing should follow the 
general pattern prescribed for the staff estimate being presented. 

BRIEFING PROCEDURES 

11-31. There are four steps for executing a briefing assignment— analyze the 
situation, structurethe briefing, deliver the briefing, and follow up. 

NOTE: All junior -grade NCOs should have received some formalized speech training as 
part of their NCO professional development. However, this training is not always 
adequate. Most installations have courses available such as instructor training or 
public speaking. These are generally short courses that will aid an NCO in presenting 
briefings. 

ANALYZE THE SITUATION 

11-32. The situation analysis includes analyzing the audience and the 
occasion, determining the purpose, allocating time, reviewing the facilities, 
and scheduling the preparatory effort. 

• Audience and occasion. Consider the characteristics of the 
audience and the nature of the occasion. Include— 

Who is to be briefed and why? 

What is their official position? 

How much knowledge of the subject does the individual have? 

Before briefing an individual for the first time, inquire as to their 

desires. 

What is expected of the briefer? 

• Purpose. Understand the purpose of the briefing to be delivered. Is it 
to present facts or to make a recommendation. The purpose 
determi nes the nature of the briefing. 

• Time allocated. Know the approximate time allocated before 
constructing the briefing. The time allocated for a briefing will 
frequently dictate the style, the physical facilities, and the 
preparatory effort required. 

• Facilities. Consider the physical facilities available. For example, if 
the briefing is held in an office, the use of heavy equipment may be 
impossible. Consider the availability of visual aids and time 
constraints. 

• Preparatory effort. Schedule the preparatory effort carefully. 
Prepare a detailed presentation plan, and ensure that any assistant 
briefers know what is expected of them. Formulate a briefing 
checklist, make an initial estimate of the deadlines that must be 
established for accomplishment of each task, schedule facilities for 
rehearsal, and request critiques. 

STRUCTURE THE BRIEFING 

11-33. The structure of a briefing will vary with the type and purpose. The 
analysis provides the basis for this determination. When the briefing is to be 
informational, it will consist of such things as assembling information, 
selecting key points, deciding how to present the key points, and selecting 
visual aids. When the briefing is to obtain a decision, the briefer must state 



Reports, Briefings, and Operation Orders 11-11 



FM 3-34.331 



the problem as well as the facts and must isolate and analyze the courses of 
action, reach conclusions, make recommendations, and obtain an 
understandable decision. Follow these steps when structuring a briefing: 

Step 2. Collect material. 

Step 2. Know the subject thoroughly. 

Step 3. I sol ate the key poi nts. 

Step 4. Arrange the key points in logical order. 

Step 5. Provide supporting data to substantiate the validity of key points. 

Step 6. Select visual aids. 

Step7. Establish the wording. 

Step 8. Rehearse i n detai I . 



DELIVERTHE BRIEFING 



FOLLOWUP 



11-34. The success of the briefing depends greatly on the manner of 
presentation. A confident, relaxed, clearly enunciated, and forceful delivery 
that is obviously based on a full knowledge of the subject helps convince the 
audience. Maintain a relaxed but military bearing and deliver a briefing that 
is concise, objective, and accurate. Be aware of the following: 

• The basic purpose of the briefing is to present the subject as directed 
and to ensure that the audience fully comprehends it. 

• Brevity precludes a lengthy introduction or summary. 

• Conciseness permits no attention getters. I llustrations should be used 
for clarification if questions arise. 

• There must be no personal or emotional involvement. Use logic in 
arriving at conclusions and recommendations. 

• Interruptions and possible questions must be anticipated at any point. 
If interruptions occur, answer each question before proceeding. If the 
question will be answered later in the presentation, so state, and 
make specific reference to the earlier question when such material is 
introduced. Do not permit questions to distract from quickly getting 
back to the planned presentation, and be prepared to support any part 
of the briefing. 



11-35. Prepare an M FR when the briefing is over. The M FR should be brief, 
but it should record the subject, date, time, and place of the briefing as well as 
the rank, name, and position of those present. The substance of the briefing 
may be recorded in a concise form or it may be omitted. Recommendations and 
their approval, disapproval, or approval (with modifications) are recorded. 
Any instructions or directed action resulting from the briefing and the 
individual who is to take action are also recorded. When there is doubt as to 
the intent of the decision maker, a draft of the MFR is submitted to that 
individual for correction before it is prepared in final form. The MFR is 
distributed to staff sections or agencies that must take action on the decision 



11-12 Reports, Briefings, and Operation Orders 



FM 3-34.331 



or instructions contained in it or whose operations or plans may be influenced. 
A copy should be included in the project file. 



SECTION III - SURVEY SOP AND SUPPORTING ANNEXES 



11-36. Figures 11-1 through 11-9, pages 11-14 through 11-33, are designed to 
serve as a sample SOP for topographic-survey operations. This SOP is 
intended as a guide, and compliance with these procedures may be the 
difference between an exemplary survey project and a very intensive learning 
experience for a survey crew. One SOP cannot cover the diverse survey 
projects encountered worldwide, so adjustment will need to be made when 
required. 

11-37. This sample SOP is designed for topographic-survey operations and 
includes the following sample annexes: 

Annex A. I SVT report format. 

Annex B.TECHOPORD format. 

Annex C. Fragmentary order (FRAGO) format. 

Annex D. Percentage-of-project-completion report format. 

Annex E. End-of-project report format. 

11-38. This sample SOP is to be used as a guide for completing a survey SOP 
and the supporting annexes. Refer to current correspondence guidance for 
proper preparation and formatting of these documents. 

11-39. This SOP is important for the following reasons: 

• The formats are a guide to ensure uniformity and completeness of 
survey orders and reports. 

• A thorough reading of the content will provide insight into various 
types of surveys, the extent and depth of planning needed for surveys, 
and a means of learning from previous surveys. These sample orders 
and reports were taken from actual survey projects. 



Reports, Briefings, and Operation Orders 11-13 



FM 3-34.331 



DEPARTMENT OF THE ARMY 
Engineer Company/Section/Squad 
Engineer Battalion (Topographic) (Airborne) 

SUBJ ECT: Units' Survey-Operations SOP 

1. INTRODUCTION 

a. This SOP is designed to clarify and expedite mission accomplishment (specifically survey 
projects) so that projects are completed on time and meet specifications at a minimum cost. 

b. The tasks identified herein must be accomplished. This SOP serves as a flowchart, with 
explanations of activities, and includes formats and information flow for reports. This SOP should 
be used as a checklist and a management-control document for all levels of operation (company, 
section, and squad). 

2. PROJ ECT REQUEST AND S3TASKING. No project will be undertaken unless directed by 
the engineer battalion operations officer. All projects must be coordinated with the S3, regardless 
of the source of the request (for example, Nl MA, MACOMs, installation and community staff 
elements, or allied nations). 

3. OPERATIONS-SECTION PROJ ECT EVALUATION. The company operations section must 
evaluate the project directive and advise the company commander in the following areas: 

a. Resources. Identify the manpower and equipment requirements to complete the project as 
specified. Identify available manpower and equipment. 

b. Appropriateness. Identify if the project requires M OS 82D (surveyor) skills. Identify if the 
company currently has the expertise required for the project. 

c. Scheduling. Identify the project's priority and duration. Identify how the current work 
schedulewill be affected, how annual training requirements will be affected, and if the work can be 
done in any season. 

d. Final product. Identify what the customer really wants and needs. Identify what the 
company would have to produce. 

e. Funding. Identify how the project will be funded. Identify how much money is available 
and what may be purchased (for example, lodging, rations, office and field materials, POL, repair 
parts, and equipment rental). 

4. RESEARCH AND COORDI NATION. The NCOIC will conduct an office recon for the project. 
This recon will include— 

• Customer contact to determine the exact project requirements and the format of the final 
product. 

• Research for reference data (such as station trig lists, maps, aerial photographs, and 
climate data). Data sources may include Nl MA, USGS, NGS, the National Oceanic and 
Atmospheric Administration (NOAA), TEC, and the customer or state, county, and 
municipal records. When working in another nation, request information from the host 
nation. 

5. WARNING ORDER. The company operations section will issue a warning order to the 
appropriate platoon based on project priority requirements, existing projects, available resources, 
and training requirements. The warning order will identify project requirements and the date of 
execution. The warning order will direct a recon mission and an I SVT report (Annex A) 
(Figurell-2, pagell-22). Upon receipt of the warning order, the survey section will begin 
reporting the project's status weekly to the company operations section. 



Figure 11-1. Sample Survey SOP 



11-14 Reports, Briefings, and Operation Orders 



FM 3-34.331 



6. SQUAD ASSIGNMENT. The platoon HQ will select a squad and/or specific personnel for the 
project. This determination will be based on the availability of personnel and equipment, personnel 
experience, familiarity with the project area, and required training. 

7. ON-SITE RECON. The survey section is responsible for the initial on-site recon. A squad 
representative will assist with the recon. An ISVT report will be submitted, through the platoon 
leader to the company commander, with an information copy provided to the commander, engineer 
battalion (topographic), attention: S3. The report is normally due five working days after the 
completion of the recon and will be prepared by the squad assigned to the platoon HQ. The 
company commander will advise the battalion commander on the appropriateness of the project. 

NOTE: If no further site recon occurs between the initial on-site recon and the arrival of 
the advance party, the most likely squad leader MUST participate in the initial on-site 
recon. If this recon is for support, it must be documented. If this recon is only to 
determine acceptance of the project, another recon will be required to determine the 
survey plan and to confirm the support. 

8. OPORD. The company operations section will prepare and issue a TECHOPORD (Annex B) 
(Figurell-5, pagell-26) in the standard military five-paragraph format. TheTECHOPORD will 
direct the platoon to perform the survey mission. The company operations section will issue all 
maps, trig lists, and overlays (if not previously issued) to the survey section. 

9. FRAGO. The platoon HQ will issue a FRAGO (Annex C) (Figurell-6, page 11-27) to the 
assigned squad instructing them to perform the survey mission. The FRAGO will contain all the 
information required by the squad leader to complete the project. 

10. DETAILED RESEARCH AND COORDINATION. The squad leader is responsible for the 
detailed examination of applicabletrig lists, past project reports for the area, maps, deeds, and any 
other pertinent source data. The platoon HQ and the SIC may be tasked to assist in assembling 
this information. Using this information and any on-site-recon information, the squad leader will 
design the project. Weekly percentage-of-project-completion progress reports (Annex Dj 
(Figure 11-7, page 11-28) will be submitted through the platoon HQ to the company operations 
section from this point until project completion. The squad leader will choose the method to meet 
project specifications and time requirements and will prepare a written survey plan, to include 
drawings and overlays of survey schemes, as information permits. This plan will reflect the squad 
leader's best estimate of survey design. If a comprehensive survey recon has not been 
accomplished, the survey plan will not be final. The final plan will be designed on-site as part of 
the advance party's tasking. Any changes from the original plan will be submitted to the platoon 
HQ verbally and in writing, if so instructed. The project plan will be written in theformat of a 
project briefing. 

11. CREW AND EQUIPMENT PREPARATION. The squad leader selects personnel and 
equipment based on job requirements. The personnel are selected based on their personal 
experience, expertise, and training. The crew begins immediately to train on specific skills needed 
for the project. The squad leader will identify specific items of equipment to be used on the job and 
will ensure operational readiness, to include performing required maintenance. The squad leader 
will identify and order all required supplies for the project. 

12. PROJ ECT BRIEFING. The squad leader will brief the platoon leader and the company 
commander on the project. At a minimum, the briefing will cover the following items: 

a. Mission. Identify thefinal product and the customer. 

b. Concept of operation. Identify how the squad will complete the project. Discuss the 
following items: 

(1) Design. Identify what methods (for example, triangulation, traverse, or level) will be 
used. Identify where the lines of survey will be run. Use a map to show the existing control and the 
proposed lines of survey. 



Figure 11-1. Sample Survey SOP (continued) 



Reports, Briefings, and Operation Orders 11-15 



FM 3-34.331 



(2) Time estimate. Show a proposed work-hour estimate and indicate the departure and 
return dates. 

(3) Cost estimate. Categorize the estimated cost (for example, POL, lodging, per diem, 
and contingency) and show the total cost. 

(4) Travel. I dentify the methods of travel and the amount of travel time. 

c. Personnel and equipment requirements. Identify what personnel (skills and number) 
are required, and provide a by-name listing. Identify what major items of equipment are necessary 
and how many items are required. 

d. Service support. Identify the requirements for the following: 

• Lodging. 

• Mess. 

• Medical. 

• Equipment maintenance. 

• Materials and supplies. 

• POL. 

• Transportation. 

e. Command and signal. I dentify the reporting procedures. 

f. Training. Identify the specific MOS skills and ARTEP/MTP tasks that are required by the 
project. Identify what training is necessary to prepare the squad for project execution. 

13. TEMPORARY DUTY (TDY) PREPARATION. Thesquad will usually have 14 calendar days 
to prepare for a TDY project. The squad leader is responsible for scheduling and executing 
preparations for the squad members. The platoon leader and the first sergeant (1SG) are 
responsible for assisting in these preparations. The foil owing areas should be addressed: 

a. TDY orders. 

(1) Thesquad leader will prepare a request for orders and forward it to the platoon HQ. 
This request should include the— 

• M embers' name, rank, social security number, and security clearance. 

• Project directive number. 

• Project dates. 

• Modes of transportation. 

• Special considerations (such as authorization for telephone calls, rental vehicles, and 
extra baggage). 

(2) The platoon HQ will review the request, add any necessary information, and forward it 
tothecompany operations section. The company operations section is responsible for obtaining the 
finalized orders and returning copies to the platoon. 

b. Barracks personnel. Barracks personnel are responsible for the completion of the 
following: 

• Securing oversized and valuable items. 

• Inventorying items in their wall lockers (thesquad leader and an officer should do the 
inventory and make a copy for the individual, supply, and inside the locker). 

• Having their wall lockers banded. 

• Turning in their room keys. 

c. Health and personnel records. Personnel are responsible for picking up their medical 
and dental records, rescheduling any pending appointments, and updating their shot records. They 
are also responsible for updating their military personnel records. 



Figure 11-1. Sample Survey SOP (continued) 



11-16 Reports, Briefings, and Operation Orders 



FM 3-34.331 



d. Personal gear. Soldiers should pack appropriate items for the project-area climate. For 
example, nighttime temperatures in a desert can be30°F lower than peak daytime temperatures. 
Arrange for safeguarding of privately owned vehicles (POVs) if left behind. Prior coordination may 
allow POVs to be stored in the transportation motor pool (TMP). If a POV inspection, registration, 
or insurance renewal will be needed before the members' return, a notarized authorization for 
proxy is required before leaving. 

e. Mail. Mail will not be forwarded unless specifically requested. A statement must be filed 
with the unit's mail clerk for someone else to pick up the mail in the event that the member does 
not want it forwarded. A squad member should be designated as the mail handler. 

f. Finances. Only personnel with direct deposit areauthorized toperformTDY missions away 
from the installation. After receipt of TDY orders, a pay advance may be drawn. If flying to the 
project site, TDY orders are used to obtain a transportation request and tickets at the scheduled 
airlineticket office (SATO). Thesquad leader will brief the squad on travel -voucher procedures (for 
example, keep copies of the original orders, travel requests, lodging receipts, official telephone 
receipts, contingency purchase receipts, and rental receipts). 

g. Military drivers' licenses. Personnel must get a license for all squad vehicles and any 
possible TM P vehicles (for example, pickups or vans) that they will be required to operate. 
Personnel must take a copy of their military driver's license to the project site. 

h. Equipment inventories. Any equipment the squad leaves behind must be inventoried in 
writing. The inventory must be signed by the master hand-receipt holder or the acting squad 
leader. All equipment taken to the project site will be inventoried in writing by thesquad or team 
leader. Copies of the hand receipts should remain with the individuals that are signed for the 
equipment. 

i. Military vehicles. Each vehicle must have a thorough technical inspection before 
departure, must have a complete organization vehicle maintenance (OVM) set, and should be 
dispatched for the entire length of the project. 

j. Briefings. Thesquad leader will give a project briefing to the squad members. The platoon 
and/or company HQ will give safety and personal -conduct briefings. 

k. Sign out. All personnel will sign out of the battalion with the Adjutant (US Army) (SI) or 
the staff duty NCO (SDNCO) upon departure. Meal-card holders will turn in their meal cards. 

I. Government credit cards. All squad members will obtain a government credit card from 
the supply officer (US Army) (S4). 

m. Instrument calibration. The squad leader will ensure that all adjustments and 
calibrations for the surveying equipment to be used on the project are completed. 

n. Administrative project file. The administrative project file should include the foil owing: 

A copy of the project directive. 

A copy of the survey plan. 

A copy of the recon report. 

Copies of all subsequent trip reports. 

Copies of all TDY orders/advances related to the project. 

Emergency data on all personnel assigned to the project. 

The company's officer and NCO rosters (including telephone numbers). 

Filecopies of all required forms for reproducing additional copies. 

A copy of each member's military driver's license. 

Travel vouchers. 

A copy of the current battalion access roster. 



Figure 11-1. Sample Survey SOP (continued) 



Reports, Briefings, and Operation Orders 11-17 



FM 3-34.331 



o. GS equipment and supplies. The following GS equipment and supplies should be 
included: 

Office supplies. 

Survey and other support forms. 

A first-aid kit. 

Drawing, chart, and printer paper. 

Calculators, paper, and batteries. 

Counseling statements. 

Official mailing envelopes. 

Weekly-report forms. 

p. Reference materials. Thefollowing reference materials should be included: 

Maps and trig lists. 

Soldier training publications (STPs) and common training task (CTT) manuals. 

J ob books. 

Survey manuals. 

The company's survey SOP. 

TMs and manufacturers' manuals. 

q. Training. Training should be completed or rescheduled as necessary. Consider the 
following training requirements: 

• Annual training requirements (mission), to include weapons qualification and theArmy 
physical fitness test (APFT). 

• Annual training requirements (personal knowledge), to include CTT packets and 
scheduled training for theTDY period. 

• Weight-control program. 

• POV training (to include registration and operator's license). 

• Defensive-driving training. 

• Off-duty classes. 

r. Family members. Personnel must get a power of attorney (if needed) and make 
arrangements for nonlicensed dependents (such as commissary, hospital, and shopping privileges). 

14. ADVANCE PARTY 

a. Generally, the squad leader and one or two squad members will depart first. The assistant 
squad leader will complete the final administrative preparations with the remaining squad 
members. 

b. The squad leader will inspect and sign for quarters and administrative space at the project 
site. Telephonic communications with the company at the home site should be established upon 
arrival and equipment should be secured. If communication with the home site is required after 
duty hours, contact will be made with platoon HQ personnel at home or, as a last resort, with the 
SDNCO. 

c.AII POCs from the initial recon should be contacted. Additionally, the military or local police 
should be informed of mission requirements, AOs, vehicletypes, and bumper/license numbers. 

d. Further detailed recon/station recovery and verification should begin immediately and the 
final project design completed. Coordinate access for keys, escorts, and range-control data from 
local surveyors or the local courthouse. A successful advance party will allow the squad to begin 
work as soon as they arrive at the project site. 



Figure 11-1. Sample Survey SOP (continued) 



11-18 Reports, Briefings, and Operation Orders 



FM 3-34.331 



15. SQUAD MOVEMENT TO THE PROJ ECT 

a. The squad leader or the assistant squad leader will conduct the movement to the project. All 
vehicles will move as a group under the NCOIC's control. If the project site is 450 miles or less 
away, the movement time will be one day. At distances greater than 450 miles, the movement rate 
will be approximately 300 miles per day. All overnight lodging will beat one location if possible, 
and all equipment will be secured. 

b. Obtain fuel at service stations that accept government credit cards. Use self-service pumps 
when possible. 

c. Each day, the platoon HQ or theSDNCO will be given the location and telephone number of 
the overnight lodging. They will also be notified upon arrival at the project site. 

d. If movement is by commercial air, ensure that all baggage claim checks are safeguarded 
until all equipment is received at the final destination. If movement is by military aircraft, make 
every attempt to move the equipment with the personnel. If equipment must be moved 
independently, the equipment will be submitted with a "priority, no-bump" statement. At least one 
person will observe the physical loading of the survey equipment onto the aircraft. Copies of all 
movement documents will be retained until the equipment is received after movement. At a 
minimum, obtain and document the— 

Type and model of the aircraft. 

Tail number of the aircraft. 

Mission number. 

Number of thetransportation-control-and-movement document (TCM D). 

Date and ti me of departure. 

Route of the aircraft (including any intermediate stops before the survey equipment is 

to be unloaded). 

16. PROJ ECT EXECUTION 

a. Fieldwork. The squad leader is responsible for daily checks of fieldwork and computations. 
All recordings and computations should be in black ink, double-checked, and initialed to indicate 
that the checks have been performed. 

b. Maintenance. Daily maintenance on each vehicle and weekly preventive-maintenance 
checks and services (PMCS) on all survey equipment should be performed. Report immediately to 
platoon HQ each time the equipment-readiness status changes. All accidents must be reported to 
the company commander within 24 hours. Accident reports and statements from all concerned 
parties will be prepared immediately and forwarded to the company commander. 

c. Safety. All guidelines set forth in the unit's safety SOP must be followed. 

d. Inventories. Those items used in thefield survey and all sensitive items of equipment (for 
example, survey instruments, binoculars, compasses, and OVM) must be inventoried daily. 
I nventory weekly all hand-receipted equipment, and report any damaged, lost, or inoperational 
equipment to the platoon HQ within 24 hours. 

e. Training. The squad leader will determine the type and schedule of physical training. The 
physical training should meet current minimum standards. CTT and soldier's manuals (SMs) 
should betaken to the project because training in these skills can be conducted during inclement 
weather. 

f. Progress reports. Weekly progress reports will be submitted to the platoon HQ. The 
format shown at Annex D should be used to record vehicle mileage, fuel used, work hours 
expended, and the percent of the project completed. 

g. Daily log. The squad leader will keep a written daily log of the progress, activities, and 
problems that relatedirectlytothe mission. All other occurrences (such as personnel insubordinate 
behavior) will be recorded. The squad leader will be prepared at all times to present an informal 
progress briefing to any visitors or inspectors. 



Figure 11-1. Sample Survey SOP (continued) 



Reports, Briefings, and Operation Orders 11-19 



FM 3-34.331 



17. ON-SITE EDIT 

a. The squad is responsible for conducting an on-site edit during the last phase of the project 
(if possible). This edit will include, but is not limited to, checking— 

• Computations. Math computations and procedures must be done correctly (to include 
all headings and signatures). 

• Field sheets/books. Field notes should be checked and have headings. 

• Station descriptions. Station descriptions must include a completed sketch, 
appropriate reference features, and field-note checks. Grammar and paragraph 
sequence should be checked. 

• Airfield drawings. Airfield drawings must be complete, accurately plotted, and field 
checked. 

b. All corrections and notations made by edit personnel will be in red ink. All pages checked 
will include the editor's initials in red ink. Notes and lists should be free of any glaring or repetitive 
errors. 

18. SQUAD MOVEMENT FROM THE PROJ ECT 

a. After all field observations and computations are completed, the squad will clear the project 
site and return to the home installation. The squad leader will ensurethat— 

Borrowed equipment is turned in. 

The lodging area is cleaned. 

Equipment is inventoried. 

Preoperational vehicle checks are conducted. 

All outstanding bills are paid. 

All vehicles are properly dispatched. 

b. The customer will not be provided a copy of the unedited data unless so directed by the 
platoon/company HQ. When required to leave a copy with the customer, ensurethat a statement is 
attached indicating that the data provided is preliminary and unadjusted. 

c. Movement from the project will be conducted the same as movement to the project. The 
platoon HQ will be contacted before departure from the project site. 

19. SQUAD RECOVERY. Upon return to the home installation, the following will be 
accomplished: 

• A platoon representative will meet the returning squad with any instructions. 

• Members will sign in at the SI or theSDNCO. 

• Members will sign for keys and inventory their wall lockers. 

• Vehicles will be topped off, cleaned, technically inspected, and secured at TM P. 

• TOE equipment will be cleaned, inventoried, inspected, and secured. Any required 
maintenance will be scheduled. 

• Finance vouchers will be completed, inspected at the platoon HQ, and filed with the FAO 
for payment. 

• The platoon HQ will be briefed on the project's status. 

• Each person's final finance voucher will be forwarded through the platoon HQ to the 
company operations section when received. 

• Time for personal affairs and missed training will be scheduled. 

20. EDIT AT HQ. Upon return from the project, the squad leader will submit a completed survey 
packet to the platoon HQ. The platoon HQ will check all final computations, drafting, and 
recovery-card preparation. An end-of-project report (Annex E) (Figurell-9, pagell-30) will be 
submitted by the squad leader to the platoon HQ within three working days after the survey 
project is completed. A copy of the report should be included in the survey packet. The survey 
packet should contain (in thefollowing order) this information: 

• The end-of-project report. 

• A detailed narrative (packet introduction) explaining the contents of the packet. 



Figure 11-1. Sample Survey SOP (continued) 
11-20 Reports, Briefings, and Operation Orders 



FM 3-34.331 



A sketch or an overlay of all the work done. 

An index. 

Tabulated data and DA Forms 1959. 

Check -angle, GPS, distance, level, and starting-inverse computations. 

All level lines, traverses, and GPS data in sequence (main-control extension, connecting 

control, and side or loop extensions). 

Level lines will contain (in order) a sketch of the level line, a DA Form 1942, and field 
notes. 

* Traverses will contain (in order) a sketch of the traverse, final position computations 
(DA Forms 1923 and 1940), the final inverse position, elevation computations, 
abstracts, distance-measurement/reduction field sheets, horizontal-direction field 
notes, vertical-angle/ZD field notes, and intersection/side-shot notes. 
GPS data will contain a sketch of the GPS positions, printed position computations and 
datum transformations, and backup disks containing all recorded data. 

21. PLATOON REVIEW 

a. The platoon will review the end-of-project report and make a file of all pertinent records, 
vouchers, forms, reports, and copies of the final product. The platoon will make appropriate award 
recommendations and ensure that all members' finance transactions (for example, meal cards, 
separate rations, and basic allowance for quarters [BAQ]) are followed through to completion. 

b. Upon completion of the platoon review, a first endorsement totheend-of-prqject report will 
be prepared by the platoon and forwarded with the report and final project packet to the company 
operations section. The endorsement will identify any additional work hours expended during the 
edit and review, inspection results, and any other pertinent data. 

22. COMPANY OPERATIONS-SECTION FINAL REVIEW. The company operations section 
will review the final project packet for accuracy and completeness. A filecopy will be made and any 
pertinent data will be stored in the SIC. The project packet will be forwarded (with a letter of 
transmittal) to the battalion S3. Additionally, a second endorsement totheend-of-prqject report 
will be prepared and forwarded to the battalion S3. This endorsement will contain any additional 
work hours expended during theedit and review and inspection and all final project data. Copies of 
the end-of-project report (with all endorsements and enclosures) will be forwarded to the platoon 
HQ and the battalion S3 for information and filing. A file copy will also be kept in the company 
operations section. 



Figure 11-1. Sample Survey SOP (continued) 



Reports, Briefings, and Operation Orders 11-21 



FM 3-34.331 



DEPARTMENT OF THE ARMY 
Engineer Company 

Engineer Battalion (Topography) (Army) 
Fort Anywhere, State, and Zip 

AFFA-TA-S 03 February XXXX 

Commander 
Engineer Company 
Attention: Operations 
Fort Anywhere, State, and Zip 

Reference: Project directive number, date, FAA Airfield Obstruction Survey. 

SUBJ ECT: ISVT Report (Fort Bliss, Biggs Army Airfield [AAF], Texas, 28- 31 J anuaryXXXX) 

1. PERSONNEL 

a. List all POCs at the project site. 

b. List any other POCs involved with the project. 

2. OBJ ECTIVES 

a. Determi ne the scope of the work to be performed. 

b. M ake a thorough recon of the areas to be surveyed. Locate existing survey control. 

c. Complete a liaison for all types of support requirements ranging from lodging to vehicle 
maintenance. 

3. MISSION. The Survey Section, 99th Engineer Company, will dispatch a survey team of eight 
members to F ort Bliss, Texas, on or about 19 February XXXX, after receipt of project funding. They 
will conduct a complete survey of all NAVAIDsand airfield obstructions according to specifications 
established by the US Army Air Traffic Control (ATC) Activity, Aeronautical Services Agency, 
Cameron Station, Alexandria, Virginia, 22304-5050. If time and funding permit, the team will 
revalidate the aging compass rose located on Biggs AAF. 

4. DISCUSSION 

a. Location. Biggs AAF is located adjacent to Fort Bliss, Texas, and El Paso International 
Airport. 

b. Environmental factors. The terrain is basically flat, with the airfield being located on a 
high desert plateau. The Franklin Mountains arelocated about 4 miles west of the airfield, and the 
Hueco Mountains are located about 15 miles to the east. Vegetation is sparse and is limited to 
scrub brush. Normal daily temperatures for this time of year are 402F to 502F during the day and 
20SF to30SF at night. Precipitation is minimal throughout the year. 

c. Medical facilities. Emergency medical treatment is available 24 hours a day at the 
William Beaumont Army Medical Center. Routine treatment may be accomplished at the 
consolidated troop medical clinic located in Building 2496. Dental care will be provided (for 
emergencies only) at the dental clinic located in Building 2699. 



Figure 11-2. Sample Annex A (ISVT Report) 



11-22 Reports, Briefings, and Operation Orders 



FM 3-34.331 



d. Shopping facilities. Complete commissary and post exchange (PX) facilities are available 
on Fort Bliss. Additionally, small branch exchanges are located throughout the post and on Biggs 
AAF. Both facilities accept checks, and the PX will cash personal checks for up to $100 per day. 
Additionally, the PX will accept certain specified credit cards. 

e. Vehicle maintenance. Fort Bliss TMP is unable to support our vehicle requirements. We 
will rent two sedans and one pickup truck from the Bogus Rental Car Company, El Paso, Texas. 
Fuel will be procured through TMP with DPW reimbursing TMP for thefuel used. 

f. Lodging and office space. As of this date, the only lodging available on Fort Bliss is 
through the bachelor enlisted quarters (BEQ). Thelodging officeis located in Building 504A. Office 
and equipment-storage space is available on Biggs AAF. ThePOC is the airfield operations office. 

g. Dining facilities. The use of government mess is adverse to the timely completion of the 
mission on Fort Bliss. Access to the project site is controlled by the airfield operations office, and 
the hours of work are adjusted according to flight operations. It would cause undo delay to halt 
survey operations to meet the scheduled meal times of a dining facility. It is strongly recommended 
that all personnel be placed on per diem. There are numerous restaurants and fast-food 
establishments in the Fort Bliss and El Paso area. There is also a food concession next to the PX. 

h. Cost estimates. A cost-esti mate work sheet is at Enclosure 1 (Figure 11-3, page 11-24) and 
a cost-estimate memorandum is at Enclosure 2 (Figurell-4, pagell-25). Cost estimates should 
include the foil owing: 

• Parameters— 

* Advance party. 
Remainder of crew. 
Command visitors. 
Rental cars. 

• Actual costs— 
» Airfare. 

Lodging. 
Per diem. 
> Transportation to, on, and from the project site. 

Shipment of equipment (identify the shipping company). 
Contingency fund. 

• Total estimated cost. 

5. TECHNICAL INFORMATION (INCLUDE IF APPLICABLE) 

6. RECOMMENDATION AND CONCLUSION. The project should be accepted by this unit. It 
will provide training in thefollowing STP/MTP tasks: 

a. Task number 051-260-1122 (Set Up Survey Target). 

b. Task number xxx-xxx-xxxx (task title). 



JOHN DOE 

Sergeant First Class (SFC), US Army 

Survey-Section NCOIC 

Enclosures 



Figure 11-2. Sample Annex A (ISVT Report) (continued) 



Reports, Briefings, and Operation Orders 11-23 



FM 3-34.331 













Cost-Estimate Work Sheet 








Parameters 








Advance partv: Depart 28 Mav 1999 (number of personnel 


3 ) 




Return 4 June 1999 (number of personnel 


1 ) 


Return 7Julv1999 (number of personnel 

Remainder of crew: Depart 2 June 1999 (number of personnel 
Return 7Julv1999 (number of personnel 


2 ) 


9 ) 


9 ) 




Command visitors: Depart 22 June 1999 (number of personnel 

Return 24 June 1999 (number of personnel 
- "^[(i, "lumumiiiiiiiuuu 

""ft! 


2 ) 




2 I 












Actual costs 






Airfare: Advance partv 3 persons x $ 899.00 


= $ 2,667.00 






Crew 9 persons x $ 899.00 


= $ 8,001.00 






Visitors 2 persons x $ 899.00 


= $ 1,778.00 






Total 


= $12,446.00 






Lodging: Advance party 2 P ersons x 40 davs x 

$25.00 








Advance party 1 Persons x 6 days x 

$25.00 

Crew g persons x 36 davs x 


= $ 2.000.00 
= $ 150.00 






$25.00 
Visitors 2 persons x 2 days x 


= $ 8.100.00 






$25.00 


= $ 100.00 






Total 


= $ 22,796.00 






Per diem ($49.50 per day) 


= $22,176.00 






Total 


= $ 44.972.00 






Transportation to the site (provided by local personnel) 


= $ 0.00 






Shipment of equipment (identify the company) 


= $ 3,100.00 






Contingency fund 


= $ 3,000.00 






Total cost 


= $51,072.00 













Figure 11-3. Sample Enclosure 1 to Annex A (Cost-Estimate Work Sheet) 



11-24 Reports, Briefings, and Operation Orders 



FM 3-34.331 



DEPARTMENT OF THE ARMY 
Engineer Company 
Engineer Battalion (Topographic) 
Fort Anywhere, State, and Zip 

(office symbol) 31J anuaryXXXX 

Commander 

United States Army Air-Defense Center and Fort Bliss (USAADCENFB) 

Attention: ATZC-DPW-P 

Fort Bliss, Texas 79916-6104 



SUBJ ECT: Biggs AAF Survey Cost Estimate 



1. After performing a thorough recon for this project, I estimate the cost for this project to be 
$51,000.00. This cost estimate reflects the fact that no vehicle support or free lodging are 
available from Fort Bliss. 

2. This cost estimate does not reflect the amount that DPW will need to reimburse the Fort 
Bliss TMP for about 200 gallons of gas. This fuel will be needed for use by the three rental 
vehicles to be used on this project. 

3. A funding request for the amount of the cost estimate should be prepared and forwarded to: 
Commander, Engineer Battalion (Topographic), Attention: AFFA-TA-PCS, Fort Anywhere, 
State, and Zip. Request this action be expedited to allow the project to begin on 
19 February XXXX. 



JOHN DOE 
SFC, US Army 
Survey-Section NCOIC 



Figure 11-4. Sample Enclosure 2 to Annex A (Cost-Estimate Memorandum) 



Reports, Briefings, and Operation Orders 11-25 



FM 3-34.331 



Engineer Battalion (Topographic) 
Fort Anywhere, State, and Zip 

References: 

a. Letter, dated 17 MayXXXX, SUBJ ECT: Engineering Surveys of AAFs 

b. Letter, dated 29 MayXXXX, SUBJ ECT: Engineering Surveys of AAFs 
Time zone used throughout this order: ROMEO 

SUBJ ECT:TECHOPORD (Fort Bliss) 

1. SITUATION 

a. Enemy forces. None. 

b. Friendly forces. DPW, Fort Bliss, Texas, Engineer Battalion (Topographic) (Airborne) 
with subordinate units (H HC and Engineer Company [Topographic]). 

c. Attachments and detachments. None. 

2. MISSION. The engineer company (topographic) will perform a NAVAI D/obstruction survey 
of Biggs AAF, which is adjacent to Fort Bliss, Texas. 

3. EXECUTION 

a. Concept of operation. The engineer company (topographic) will coordinate, schedule, 
and perform survey operations to accomplish the above mission not later than 30 April XXXX. 
The S3 will monitor project progress and coordinate external requirements upon request. 

b. Coordinating instructions. Direct coordination with the following POC is 
authorized: First Lieutenant (1LT) Gibson, Master Planners Office, DPW, Fort Bliss, Texas, 
555-555-5555. 

4. SERVICE SUPPORT 

a. Unit equipment and supplies will be used. Rental vehicles are authorized if 
economically feasible. 

b. Support request(s) will be submitted to this HQ, Attention: AFFA-TA-OP, as needed. 

5. COMMAND AND SIGNAL 

a. Command. Refer to the battalion's SOP and complete thefollowing reports. 

(1) Submit a recon report within 30 days of receipt of this OPORD to the S3. 

(2) Report the project's status weekly to the S3 not later than 1200 hours each F riday. 

(3) Submit an end-of-project report to the S3 within 15 days after completion of the 
project. 

b. Signal. None. 



WILLIAM SMITH 

Lieutenant Colonel (LTC), Engineer (EN) 

Commanding 



Figure 11-5. Sample Annex B (TECHOPORD) 



11-26 Reports, Briefings, and Operation Orders 



FM 3-34.331 



F RAGO #99-2009-1 

References: 

a. Technical Operations Work Order #99-2009 

b. F M 3-34.331 

c. STP 5-82D14-SM -Trainer's Guide (TG), Task #051-260-XXXX 
Time Zone Used Throughout the Order: ROM EO 

SUBJ ECT: FRAGO (Fort Bliss) 

1. SITUATION 

a. Friendly forces. Engineer battalion (topographic). 

b. Enemy forces. None. 

c. Assumptions. This unit may be tasked to perform high-order survey work in the near 
future. Personnel should become familiar with the computations associated with this type of 
work. 

2. MISSION. Each squad within the survey section, engineer company, has been tasked to 
compute the geodetic azimuth from the north and the geodetic distance for each set of known 
coordinates to be used during the survey. 

3. EXECUTION 

a. Concept of operations. 

(1) Transcribe the positions for each set of known coordinates onto DA Form 1923. 

(2) Compute the geodetic azimuth from the north and the geodetic distance for each 
set of coordinates. 

(3) Compute the distance to 0.001 meter and the azimuth to 0.01". 

(4) Comply with third-order, Class I traverse specifications. 

(5) Maximize the use of personnel that are unfamiliar with this computation for 
training purposes. 

(6) Submit progress reports (to include the work hours expended and a by-namelist of 
the personnel working on computations) by 1100 hours each Friday until the completion of the 
project. 

(7) Submit the completed data to the survey-section NCOIC by the close of business 
27 February XXXX. 

b. Coordinating instructions. Calculators and reference materials are available from 
SFC Doe. All technical questions/problems should be directed to SFC Doe. 

4. ADMINISTRATION AND LOGISTICS. The only available resources are those contained 
within the survey section. 

5. COMMAND AND SIGNAL 

a. Command. Squad leaders are responsible to ensure that all required data and reports 
reach the survey-section NCOIC as required. 

b. Signal. None. 

JOHN DOE 
SFC, US Army 
Survey-Section NCOIC 



Figure 11-6. Sample Annex C (FRAGO) 

Reports, Briefings, and Operation Orders 11-27 



FM 3-34.331 



26 February XXXX 
MEMORANDUM FOR SEE DISTRIBUTION 
FROM Commander, Engineer Company (Topographic), Fort Anywhere, State, and Zip 

SUBJ ECT: FA-TA-S Survey Project, Percentage of Completion 

1. To standardize company operating procedures, projects will be reported using a survey-project 
timeline that lists the percentage of completion for each project task. 

2. The project's status is due to the company operations section each Friday by 1000 hours. 
Request immediate attention be given to this suspense. 

3. A sample survey-project timeline is enclosed. 

4. The field-survey percentage-of-project-completion timeline is broken down for each project task 
and is reported as follows: 

Traverse for extension of control . 

Level line for control extension or cross sections/profiles. 

GPS point positioning. 

Airfield obstructions or NAVAI Ds. 

Drafting. 



MARY DOE 
Captain (CPT), EN 
Commanding 



Enclosure 



Figure 11-7. Sample Annex D (Percentage-of-Project-Completion Report) 



11-28 Reports, Briefings, and Operation Orders 



FM 3-34.331 











TASK 


SURVEY-PROJECT TIMELINE (DAYS) 






1 


2 


3 


4 


5 


6 


7 


8 


9 


10 


11 


12 


13 


14 


15 


16 


17 


18 


19 


20 


21 


22 


23 


24 


25 


26 


27 


28 


Travel and 
administration 


8 


8/ 
5 




































8 


8/5 



















Monumentation 






8 























































Level line 






1 


1 


1 


1 

















































GPS-data 
collection 








4 


4 


4 

















































Runway profiles 

















1 












































Obstructions/ 
side shots 

















2 


2 


2 


2 


2 


2 





2 


2 










n 
















Computations 

















6 


6 


6 


6 


6 


6 





6 


6 


6 


6 























Checks and 
reobservations 

















4 


1 

















2 


2 























Drafting* 


















6 


ts 


6 


6 


r> 




6 


6 


6 


6 










































































































































































































LEGEND- = Day off 2 = AISI 4 = GPS 6 = PC 

1 = Level 3 = Transit 5 = Vehicles 8 = Personnel 

*To be completed at the home station. 









Figure 11-8. Sample Survey-Project Timeline 



Reports, Briefings, and Operation Orders 11-29 



FM 3-34.331 



DEPARTMENT OF THE ARMY 
Engineer Company (Topographic) 
Engineer Battalion (Topographic) 
Fort Anywhere, State, and Zip 

AFFA-TA-X 18 April XXXX 

THRU Commander, Engineer Company (Topographic), Fort Anywhere, State, and Zip 

TO Commander, Engineer Battalion (Topographic), Fort Anywhere, State, and Zip 

References: 

a. Letter, dated 29 September XXXX, Topographic Survey Requirements (Enclosure 1) 

b. Letter, dated 10 November XXXX, Topographic Support, Project Directive #2-84 (Enclosure 2) 

c. OPORD, Engineer Battalion (Topographic), dated 30 November XXXX, OPORD 99-148 
(Enclosure 3) 

d. Letter, dated 4 October XXXX, Preliminary-Recon Trip Report (Enclosure4) 

e. Letter, dated 22 December XXXX, Recon Trip Report (Enclosure 5) 

f. Letter, dated 24 February XXXX, Inspection Trip Report (Enclosure 6) 

g. Letter, dated 12 March XXXX, Inspection Trip Report (Enclosure 7) 



SUBJ ECT: End-of-Project Report (New Cumberland Army Depot [NCAD], Pennsylvania, 
19January- 2 April XXXX) 

1. PERSONNEL 

a. I nspectors. 

SFCJ ohn Doe, Survey-Section NCOIC, 2 February 
1SG J ohn Smith, 16 - 17 February 

b. Field crew. 

Staff Sergeant (SSG)J ohn Lopez, Squad Leader, 19 J anuary- 2 April 

Sergeant (SGT)J ohn Evans, Computer, 19 J anuary- 2 April 

Private First Class (PFC)J ohn Payne, Computer/Drafting, 19 J anuary- 2 April 

Specialist (SPC)J ohn Green, Field-Crew Chief, 19J anuary- 2 April 

SPC J ohn Black, Surveyor, 19 J anuary - 2 April 

PFCJ ohn Parker, Surveyor, 19 J anuary - 2 April 

PFC J ohn Kramer, Surveyor, 19 J anuary - 2 April 

PFCJ ohn Simpson, Surveyor, 2 February - 2 April 

PFCJ ohn Gonzalez, Surveyor, 19 J anuary - 5 February 



Figure 11-9. Sample Annex E (End-of-Project Report) 



11-30 Reports, Briefings, and Operation Orders 



FM 3-34.331 



2. REQUIREMENTS 

a. The original requirements for the project were— 

• To perform a verification survey of the entire boundary. The missing corners were to be 
monumented by DPW, facilities engineering division (FED). 

• To apply third-order elevations on the boundary monuments. 

• To develop topographic maps of the two areas where Buildings 87 and 92 would be 
relocated. 

b. After thefinal recon was completed, the requirements had been changed to— 

• Perform a verification survey of the entire boundary. The missing corners were to be 
monumented by the survey crew with monuments premade by DPW, FED. 

• Apply third-order elevations on the boundary monuments. 

• Provide a drawing of the base boundary and station descriptions for each corner and 
BM (the development of topographic maps was no longer necessary). 

c. As the project neared its end and the monuments for the boundary corners were still not 
made, the requirements for elevations on each boundary monument changed to establishing BMs 
near the boundary corners (for example, nails in headwalls) and on as many boundary monuments 
as time would permit. All other requirements remained the same as stated above. 

3. METHODS. The mission was broken down into five main areas— recon, traversing, locating 
corners and placing monuments, leveling, and computing and drafting. 

a. Recon. The recon was conducted about one month in advance of beginning the fieldwork. It 
consisted mainly of a deed search at the courthouse, requests for additional information from 
adjoining landowners (for example, the Pennsylvania Turnpike Authority), an on-ground search 
for existing boundary corners and starting control, and logistical -support arrangements. This 
phase of the operation resulted in a reciprocal request from the Pennsylvania Turnpike Authority 
for two copies of thefinal drawings. 

b. Traversing. All traverse work was performed using third-order, Class I procedures. I n 
total, there were seven traverses, one of which was the main-control traverse. It contained 25 
stations and was run from Station Alpha (a first-order horizontal -control point) through boundary 
corners number 4, 5, and 6 and Stations T-4 and T-5 and closed on Station Bravo (a second-order 
point). This established a common coordinate system for the existing boundary corners. The other 
traverses were used to place control near the location where the remaining boundary corners 
should have been. The azimuths were checked and verified by performing astronomic-azimuth 
observations to third-order specifications at Station Alpha and at Stations T-4 and T-5. The main- 
control traverse had a position closure of 1:17,000, and the poorest closure obtained on any of the 
other six traverses was 1:5,000. 

c. Locating corners and placing monuments. The lost/destroyed boundary corners were 
recovered or replaced. Coordinates were computed for all boundary corners using the coordinates 
established on boundary corners 4, 5, and 6 and the bearings and distances from the deeds. 

I nverses were computed from the traverse stations nearest the desired corner to that boundary 
corner. The traverse station was occupied, the computed angle was turned, and the distance was 
horizontally taped, thus locating the corner in question. This point was then temporarily marked 
by either a piece of rebar, a railroad spike, or a nail, depending on the type of ground encountered. 
Plumbing benches were built over the temporary marks, the markers were removed, holes were 
dug, and the monuments were placed in their proper positions. After the dirt was tamped down 
and the plumb was checked, concrete collars were poured around the monuments to ensure that 
they would not move. 



Figure 11-9. Sample Annex E (End-of-Project Report) (continued) 



Reports, Briefings, and Operation Orders 11-31 



FM 3-34.331 



d. Leveling. The requirement for third-order elevations was met by running two third-order 
lines. The first line started on BM 2 and ran around the perimeter of the southern half of the depot 
toBM 1. This line established 13 BMs, had an error of closure of 0.065 feet, and was 4.8 miles long. 
The second line started on BM 1 and ran around the perimeter of the northern half of the depot 
to Station T-4. This line established the elevation on seven points, had an error of closure of 
0.003 feet, and was 1.7 miles long. 

e. Computing and drafting. Computing for this project was an ongoing endeavor from the 
time of the final recon until two weeks after the end of the project. This was due to the vast number 
of deeds for the land surrounding and now comprising the NCAD, and some of the final data was 
needed on site at the completion of the project. The drafting was accomplished in the last two 
weeks of the project and consisted of three drawings. Copies of all drawings were provided to the 
FED and the Pennsylvania Turnpike Authority before departing the NCAD. Station descriptions 
were an ongoing effort throughout the project. 

5. EQUIPMENT. Two categories of equipment were used— organizational and borrowed. 

a. Organizational. The organizational equipment included three M998 vehicles, two 
theodolites (one military level and one infrared EDME), two Philadelphia rods, twoT-2 target sets, 
one 50-meter tape measure, one 100-foot tape measure, one tape tension handle, one taping-pin 
set, and one programmable calculator. 

b. Borrowed. The following items were borrowed from the NCAD, FED: three FM, hand-held 
radios; one posthole digger; and one auger truck with operators. On two or three occasions when 
the vehicles weredown, a carryall was borrowed fromTMP. 

6. ACHEIVEMENTS. Excellent training was gained by all personnel in traverse, leveling, taping, 
and monument-setting procedures. All personnel gained valuable experience at operating under 
extreme cold and wet conditions. SGT Evans and PFC Payne received valuable experience in all 
types of survey computations, to include curve layouts. SPC Green gained experience as a field- 
crew chief. The FED gained much needed field data that should prove useful any time projects 
requiring survey data are undertaken by their office. In addition, all personnel assigned to the 
project and the engineer company (topographic) were awarded a certificate of appreciation from 
the depot commander. 

7. TECHNICAL DIFFICULTIES. Most of the technical problems encountered were a direct 
result of the vast number of deeds involved. Many of those deeds listed magnetic bearings, while 
others used true bearings. Ordinarily this would have been no problem, but the catch was that out 
of all the deeds, only two specified what type of bearings they were listing. This left a large jigsaw 
puzzle with many variables. It became a matter of trial and error until the crew was finally able to 
get the boundary to close on itself. Another problem encountered was that one of the reference 
drawings provided by FED had the numbers within a given distance transposed; that is, 1,307 feet 
was really 1,370 feet. Additional problems were encountered when the only EDM E went down and 
no replacement was available. The problems encountered in this area were due directly to a lack of 
training in taping procedures. This problem was resolved after about two days of intensive on-site 
training. 

8. ADMINISTRATIVE/OTHER PROBLEM AREAS. The largest single problem encountered 
was the vehicle-maintenance support. The support that was promised verbally by the NCAD, TMP 
never developed. It is strongly recommended that a written agreement be established during the 
recon phase of all future projects. As for the problems encountered with the vehicles (for example, 
not starting or faulty exhaust systems), it is unclear how they could have gone through a complete 
maintenance check before departing for the project and still be in such a poor state of repair. The 
only other real problem encountered was the repeated adverse weather. I n total, 13 work days 
were lost to snow, ice, rain, or fog. 



Figure 11-9. Sample Annex E (End-of-Project Report) (continued) 



11-32 Reports, Briefings, and Operation Orders 



FM 3-34.331 



9. SUMMARY. All in all, this was an excellent project. It fulfilled a vast amount of training 
requirements in a wide variety of skills. Weaknesses in the equipment department became very 
obvious. These weaknesses included a need for hand-held radios, medium- or long-range EDME, 
and four-wheel -drive vehicles. 



JOHN LOPEZ 
SSG.USArmy 
Squad Leader 



Enclosures (not included with this sample) 



Figure 11-9. Sample Annex E (End-of-Project Report) (continued) 



Reports, Briefings, and Operation Orders 11-33 



Appendix A 

Mensural Conversion Charts 

This appendix complies with current army directives, which state that the 
metric system will be incorporated into all new publications. Table A -1 is a 
metric conversion chart and Table A-2 shows conversion factors for 
temperature, angles, and time. 

Table A-1. Metric Conversion Chart 



US Units 


Multiplied By 


Equals 
Metric Units 


Metric Units 


Multiplied By 


Equals 
US Units 


Length 


Inches 


2.5400 


Centimeters 


Centimeters 


0.39370 


Inches 


Inches 


25.4001 


Millimeters 


Millimeters 


0.03937 


Inches 


Feet 


0.3048 


Meters 


Meters 


3.28080 


Feet 


Yards 


0.9144 


Meters 


Meters 


1.09360 


Yards 


Miles 


1.6093 


Kilometers 


Kilometers 


0.62140 


Miles 


Miles, Nautical 


1.8532 


Kilometers 


Kilometers 


0.53960 


Miles, Nautical 


Area 


Square miles 


2.590 


Square 
kilometers 


Square 
kilometers 


0.38500 


Square miles 


Volume 


Gallons 


3.7854 


Liters | Liters 


0.26420 


Gallons 


Mass (Weight) 


Pounds 


0.4536 


Kilograms | Kilograms 


2.20460 


Pounds 



Table A-2. Temperature, Angle, and Time Conversion Chart 



Units 


Multiplied By 


Equals 1 Units 


Multiplied By 


Equals 


Temperature 


Degrees (F) - 32 


0.5556 


Degrees (C) 1 Degrees (C) + 17.8 


1.8000 


Degrees (F) 


Angle 


Degrees 
(angular) 


17.7778 


Mils 


Mils 


0.0562 


Degrees 

(angular) 


Time 


Seconds 


0.001 


Milliseconds 


Milliseconds 


1,000 


Seconds 


Seconds 


0.000000001 


Nanoseconds 


Nanoseconds 


1 ,000,000,000 


Seconds 



Mensural Conversion Charts A-1 



Appendix B 

Control-Survey Standards 

This appendix is designed as a quick reference for platoon leaders. It 
summarizes the standards for control surveys that were discussed in 
Chapters 6, 7, and 8. 

DIFFERENTIAL LEVELING 

B-l. Differential leveling is the conventional method of leveling for the 
propagation of orthometric heights. TableB-1 and Tables B-2 and B-3, 
pages B-2 and B-3, show the overall standards and specifications for 
differential leveling. 

TableB-1. Equipment Standards 



Requirement 


Order and Class 


1st, I 


1st, II 


2nd, I 


2nd, II 


3rd 


Level 


0.2 mm/km 
spirit level 


0.4 mm/km 
electronic bar 
code 


Automatic level 
with parallel- 
plate 

micrometer or 
0.4 mm/km 
electronic bar 
code 


0.8 mm/km 
automatic level 
with parallel- 
plate micrometer 
or electronic bar 
code 


3-wire 

automatic 

level 


Staff construction 


Rigid invar 


Rigid invar 


Rigid invar 


Rigid invar 


Wood or 
metal 


Staff graduation interval (mm) 


5 


5 


5 or 10 


5 or 10 


10 


Tripod construction 


Rigid 


Rigid 


Rigid 


Rigid 


Rigid 


Bubble attached to staff 


Yes 


Yes 


Yes 


Yes 


Yes 


Solid, portable change points 


No 


No (route is 
premarked) 


Yes 


Yes 


Yes 


Umbrella for level 


Yes 


Yes 


Yes 


Yes 


No 



Control-Survey Standards B-1 



FM 3-34.331 







Table B-2. 


Equipment Testing 






Requirement 


Order and Class 


1st, I 


1st, II 


2nd, I 


2nd, II 


3rd 


System test before 
commencement 


Yes 


Yes 


Yes 


Yes 


Optional 


Maximum standard error in the 
line of sight (mm/m) 


0.05 


0.05 


0.05 


0.05 


0.1 


Vertical 

collimation 

check 


Frequency 


Daily 


Daily 


Daily 


Daily 


Daily 


Maximum 
collimation error 
(mm/m) 


0.02 


0.02 


0.02 


0.02 


0.04 


Level cross-hair verticality check 


Yes 


Yes 


Yes 


Yes 


Yes 


Staff calibration standard 


N 


N 


N 


M 


M 


Time between calibration (years) 


1 


1 


NA 


NA 


NA 


Staff bubble verticality to be within 


10' 


10' 


10' 


10' 


10' 


LEGEND: 

M = Manufacturer's standard 
N = National standard 



B-2 Control-Survey Standards 



FM 3-34.331 



Table B-3 


. Observation and Reduction Requirements 




Requirement 


Order and Class 


1st, I 


1st, II 


2nd, 1 


2nd, II 


3rd 


Instrument leveled by an 
unsystematic method 


Yes 


Yes 


Yes 


Yes 


Yes 


Leap-frog system of progression 
used 


Yes 


Yes 


Yes 


Yes 


Yes 


Staff readings recorded to nearest 
(mm) 


0.01 


0.01 


0.1 


0.1 


1 


Temperature recorded 


Start, 

middle, 

finish 


Start, 

middle, 

finish 


At start and finish of each leveling run and 
at pronounced changes of temperature 


Maximum length of sight (m) 


50 


60 


60 


70 


90 


Minimum ground clearance of line 
of sight (m) 


0.5 


0.5 


0.5 


0.5 


0.5 


Backsight and foresight lengths to 
be equal within (m) 


2 


5 


5 


10 


10 


Observation time 


Before 
1000 and 
after 1400 


Before 
1000 and 
after 1400 


Before 1 000 
and after 
1400 


Any time, provided 
atmospheric conditions allow 
positive resolution of staff 
graduation 


Two-way leveling 


Yes 


Yes 


Yes 


Yes 


Yes 


Even number of instrument setups 
between BMs 


Yes 


Yes 


Yes 


Yes 


Yes 


Maximum section misclosure 
(mm) 


37km 


47km 


67km 


87km 


127km 


Maximum loop misclosure (mm) 


47km 


57km 


67km 


87km 


127km 


Minimum number of BMs 


3 


3 


3 


3 


3 


Double-leveled BM 


Yes 


Yes 


Yes 


Yes 


Yes 


Maximum BM misclosure (mm) 


47km 


57km 


67km 


87km 


127km 


Orthometric correction 
(collimation) to be applied 


Yes 


Yes 


Yes 


Yes 


Yes 



HORIZONTAL-ANGLE MEASUREMENT 



B-2. The observation requirements for horizontal-angle measurements are 
shown in TableB-4, pageB-4. Adherence to these requirements should ensure 
that the appropriate level of precision is achieved. 



Control-Survey Standards B-3 



FM 3-34.331 



Table B-4. Observation Requirements 











Order and Class 




1st 


2nd, I 


2nd, II 


3rd 


3rd, II 


Required 
time of day 


2 hours either side of sunrise/set 
Any time except 1 200 to 1 500 
Any time (subject to checks) 


Yes 
NA 
NA 


Yes 
NA 
NA 


NA 
Yes 
NA 


NA 
NA 
Yes 


NA 
NA 
NA 


Instrument least count 


0.2" 


0.2" 


1.0" 


1.0" 


1.0" 


Horizontal zero settings 


0.2" theodolite 
1" theodolite 


Yes 
NA 


Yes 
Yes 


NA 
Yes 


NA 
Yes 


NA 
Yes 


Sets 


Minimum number of positions (horizontal) 
Number observations (vertical) 


16 
3 


16 
3 


8 1 /12 2 
2 


4 
2 


2 
2 


Field 
checks 


Horizontal 


Ranges between each set: 
standard deviation of mean 
should never exceed 


0.4" 


0.5" 


0.8" 


1.2" 


2.0" 


Ranges within each set: 
standard deviation of mean 
should never exceed 


4" 


4" 


5" 


5" 


5" 


Vertical 


Number of observations 
Maximum spread 


3 

10" 


3 

10" 


2 

10" 


2 

10" 


2 

20" 


Infrared 
distance 


Number of observations 


10 


10 


10 


10 


10 


Minimum number of network control points 


4 


3 


2 


2 


2 


Azimuth closure (arc seconds) 


1.7 JR 


37N 


4.57N 


io7n 


127N 


Closure ratio 


1:100,000 


1:50,000 


1:20,000 


1:10,000 


1:5,000 


Position closure 


0.047km 


0.087km 


0.20 7km 


0.40 7km 


0.80 7km 


1 lf using a 0.2" theodolite. 
2 lf using a1" theodolite. 

LEGEND: 

N = number of stations 



TRIGONOMETRIC OBSERVATIONS 



B-3. Trigonometric observations are used to determine trigonometric 
elevations. To achieve a desired order of trigonometrical elevation, use the 
procedures and standards for the particular observation type (for example, 
vertical angle or distance) unless specified otherwise in TableB-5. 



B-4 Control-Survey Standards 



FM 3-34.331 





Table B-5. 


Observation Requirements 




Requirement 


Order 


1st 


2nd 


3rd 


Simultaneous reciprocal 


Yes 


Yes 


Optional 


Nonsimultaneous reciprocal 


NA 


Yes 


Optional 


One-way observation 


NA 


NA 


Yes 


Observation time 


>16 km 


1400 to 1600 


1400 to 1600 


1400 to 1600 


<16 km 


1000 to 1600 


1000 to 1600 


1000 to 1600 


Number of sets 


2 


2 


1 


Number of pointings (per set) 


6 


6 


6 


Maximum range per set (in) 


6 


6 


8 


Meteorological observation 


Yes 


Yes 


Yes 



GPSTECHNIQUES 



B-4. There are two fundamental GPS techniques— relative and absolute- point 
positioning. The recommended practices for the GPS refer only to relative 
positioning. Relative positioning requires two or more GPS receivers. The two 
fundamental types of GPS receivers are navigational and survey (or geodetic). 
The receivers are distinguished by the accuracy level and type of 
measurements taken during surveys. Many receivers are capable of a number 
of measurement types. Pseudorange and carrier-phase measurements are the 
two fundamental types of measurements made with GPS receivers. 



RELATIVE-POSITIONING TECHNIQUES 



B-5. Relative-positioning techniques can be divided into two main groups- 
static and kinematic. The fundamental difference is that kinematic 
techniques require maintaining lock throughout the survey after ambiguity 
resolution. These static and kinematic techniques employ carrier-phase 
measurements. Since a carrier-beat-phase measurement is the only type that 
offers a sufficient precision in geodetic positioning at third order and higher, 
the use of receivers that measure the carrier phase is mandatory. Static and 
kinematic techniques can be grouped as follows: 

• The static group can be divided into the following techniques: 

Static (also referred to as classic static). 

Pseudokinematic (for example, intermittent static, pseudostatic, 

or reoccupation kinematic). 

Rapid static (also referred to as quick static or fast static). 

• The kinematic group can bedivided into the following techniques: 

Stop-and-go kinematic (also referred to as intermittent kinematic 

or semi kinematic). 

Kinematic (also referred to as continuous kinematic). 

OTF/ (also referred to as ambiguity-resolution OTF). 

B-6. A third group of relative-positioning techniques is based on pseudorange 
measurements. These techniques, either in postprocessed or real-time modes, 



Control-Survey Standards B-5 



FM 3-34.331 



are referred to as DGPS and aregenerally not used for precise control surveys. 
DGPS is used for accuracies of 2 to 5 meters. Precise DGPS is used for 
accuracies of 1 meter or less. 

B-7. By combining carrier-phase measurements with pseudorange 
measurements, it is possible to reach higher accuracies with DGPS 
techniques. While GPS measurements are receiver dependent, the selection of 
observation techniques is dependent on the precision required and the 
reduction process to be used. 



NETWORK DESIGN AND GEOMETRY 



B-8. When planning a GPS-S, the first step is to choose the appropriate 
technique for the precision required. TableB-6 provides a guide for what 
technique to use to achieve a particular order and class of survey. TableB-7 
provides references to the order and class of survey. 

Table B-6. Positioning Techniques 



Technique 


Order and Class 


1st 


2nd, I 


2nd, II 


3rd 


Static 


Yes 


Yes 


Yes 


Yes 


Rapid static 


NA 


NA 


Yes 


Yes 


Pseudokinematic 


NA 


NA 


NA 


Yes 


Stop and go 


NA 


NA 


NA 


Yes 



B-9. The location and distribution of points in a GPS-S do not depend 
significantly on factors such as network shape or intervisibility but rather on 
an optimum layout with sufficient redundancy for carrying out the intent of 
the survey. The intent of the network design should be to— 

• Locate new points so that the line of sight between them is clear 
(when possible). 

• Provide error control in the minimum-constraint solution (to enable 
data validation) and analysis of the accuracy of the survey. 

• Producetie-offs for integrating the survey into previously established 
control . 

• Locate ties to points with existing orthometric heights. 

B-10. Redundancies play an important role in fulfilling this intention. All 
GPS-Ss must be connected to theexisting control, theNGS, or the local project 
to ensure survey integration, legal tractability, and quality assurance. If 
established control stations are not available in the vicinity of the survey, 
bring control to the appropriate accuracy by using GPS or conventional 
techniques. When selecting established stations to connect to, give preference 
to the highest order of the nearest, established permanent marks (or geodetic 
stations) that are easily accessible. Connection should be made to a minimum 
of three points with suitable MSL heights, preferably enclosing the survey, 
and a minimum of two points with established (horizontal) coordinates. 
Additional points are to be connected to obtain quality control, with preference 



B-6 Control-Survey Standards 



FM 3-34.331 



Table B-7. Positioning References 



Reference 


Order and Class 


1st 


2nd, I 


2nd, II 


3rd 


Minimum station spacing 1 (km) 


5 


1 


0.5 


0.2 


Typical station spacing 2 (km) 


100-500 


10-100 


0.5-10 


0.1-5 


Independent 
occupations 
per station 3 


at least 3 times 
(% of total stations) 


50% 


40% 


20% 


10% 


at least 2 times 
(% of total stations) 


100% 


100% 


100% 


100% 


Minimum common satellites 


4 satellites 


Minimum PDOP required 


Less than 10 after resolution of ambiguities 


Minimum satellite elevation 


15° 


Data rate 


Optional 


Minimum observation period (static) 4 


120' 


60' 


45' 


30' 


Minimum independent baselines at 
each station 


3 


3 


2 


2 


1 The values relate to the use of conventional equipment and proprietary software. 

independent occupations per station may be back to back, but the antenna should 
be reset for each occupation. Antenna heights are to be changed by at least 0.1 to 
0.2 meter unless set up on a pillar. The fully specified minimum-observation time 

should be met with each occupation. 

3 For example, for a second-order, Class II network, aim for 20 percent of stations to 

be occupied at least three times and 100 percent of stations to be occupied at least 

twice. 

4 As a rule, 30 minutes as a definitive minimum plus about 2 minutes per kilometer. 



given to coordinated marks that enclose the surveyed area and height points 
spaced throughout the area. A least-squares adjustment of the control survey 
must be performed. 

B-ll. The planning of the observations should be such that the error budget is 
sufficiently minimized. Consider the error budget of a double difference, which 
consists of error sources affecting measurements; error sources that depend 
upon the site and the type of instrumentation used; and error sources 
resulting from reduction, adjustment, and transformation. 

B-12. Error sources that affect measurements are tropospheric refraction, 
ionospheric refraction, and orbit errors. The main error sources affected by the 
site's location and the instrumentation are centering and antenna-height 
accuracy, antenna-phase center variation, 3D differential -antenna offset, 
multipath and imaging errors, differential tropospheric delay, and differential 



Control-Survey Standards B-7 



FM 3-34.331 



ionospheric delay when using single-frequency solutions. The main error 
sources resulting from reduction, adjustment, and transformation are the 
selection of the wrong ambiguities, insufficient redundancy for quality control 
of the transformation solution, and a geoid model that is too simple or based 
on too sparse data. 



REDUNDANCY 



B-13. Redundancy in the observations is the best way of dealing with most of 
the error sources. Specific observing procedures and differencing techniques 
can eliminate other error sources that are more systematic. Error sources are 
reduced by careful site selection, averaging, and sufficient observation time to 
allow geometry change. Night observations or the use of dual-frequency 
receivers can minimize ionospheric errors. Antenna offset can be minimized 
by ensuring identical antenna orientations. Orbit errors are minimized by the 
use of precise ephemerides. 

B-14. The concept of redundancy (when using a GPS) refers to such things as 
the following: 

Increasing the percentage of points with multiple occupations. 

Tying multiple baselines into one point. 

Observing common baselines between figures. 

Closing onto existing control. 

Computing the polygon closure using data derived from different 

sessions. 

Observing morethan the minimum number of satellites. 

Averaging through observing a sufficient number of epochs. 

B-15. I ndependent reoccupation of the same point (after a sufficient lapse of 
time) to observe a different baseline is the most common way of detecting 
gross error. An alternative to independent reoccupations is the inclusion of 
conventional observations of appropriate accuracy (for example, to create ties 
between unclosed GPS polygons in the same adjustment). I n a control survey, 
all observations should be checked by the redundancies included in the 
network. The configuration of the network should involve the observation of 
closed figures, and closure polygons must combine data from different 
sessions. 



INDEPENDENT BASELINES 



B-16. An independent-baseline measurement in an observation session is 
achieved when the data used are not just different combinations of the same 
data used in computation of other baseline vectors observed in that session. In 
an observation session using five receivers, the total number of baselines can 
be computed as follows: 

Total number of baselines = = = 10 

where— 

n = the number of receivers 



B-8 Control-Survey Standards 



FM 3-34.331 



B-17. However, only four (n - 1) of those baselines are independent. The 
remainders (10 -4=6) are formed from combinations of phase data used to 
compute the independent baselines. The results from observations of the same 
baseline made in two different sessions are independent. Generally, 
independent-baseline processors assume that there is no correlation between 
independent vectors. Trivial baselines may be included in the adjustment to 
makeupfor such a deficient statistical model. If the mathematical correlation 
between two or more simultaneously observed vectors in a session is not 
carried in the variance-covariance matrix, the trivial baselines take on a 
bracing function that simulates the effect of the proper correlation statistics. 
And, at the same time, introduce a false redundancy in the count of the 
degrees of freedom. I n this case, the number of trivial baselines in an 
adjustment should be subtracted from the number of redundancies before the 
variance factor (variance of unit weight) is calculated. If this approach is not 
followed, trivial baselines will be excluded from the network altogether. 



INCORPORATION OF GPS SURVEYS 



B-18. To incorporate 3D GPS-Ss into local horizontal and vertical data 
(WGS-84 and MSL), the number, type, and distribution of control points to 
which connections should be made must be considered. A determination of 
which technique to use to derive orthometric heights from ellipsoidal heights 
is necessary. The technique will influence the choice of well-placed strategic 
points with known orthometric heights that should be observed. Alternatively, 
orthometric heights can be brought to selected points in the GPS network. 

B-19. For a small area (a few kilometers across) with a smooth geoid, solving 
for transformation parameters brings about a de facto surface fit (tilting the 
ellipsoid so that it is parallel with the geoid). When a single value for the 
geoid-spheroid separation is used at the orthometric-control points, it is 
assumed that the geoid is as smooth as the ellipsoid. For larger areas, choose 
between a geodetic-leveling, a geopotential model-based, a gravimetric, or a 
geometrically derived geoid. 

B-20. The classification of GPS results (including height) is generally 
expressed using a linear propagation method, unless requirements specifically 
call for height classification using differential leveling. I n both cases, the class 
and the order are assigned separately for horizontal and vertical control. 



SYSTEM TESTING 



B-21. A system test is recommended to qualify equipment, techniques, and 
error modeling for a particular accuracy. Evidence of a test may be required 
after acquisition of new equipment or software, when trying new techniques, 
or as justification of a chosen method of error modeling. This evidence 
serves— 

• As a justification of observing and processing techniques. 

• To validate (under similar conditions) the same equipment, the 
software, and the observation method. 

• Tojustify the error modeling. 

• As a justification of a multiplier used to increase the baseline-vector 
variance-covariance matrix elements when these are unrealistic. 

• To validate data when combining results from different equipment 
and software. 



Control-Survey Standards B-9 



FM 3-34.331 



B-22. The total GPS process is comprised of the following four distinct 
components: 

• Satellites. 

• Receiver hardware. 
Field procedures. 

• Software. 

B-23. The following procedures describe a system test that considers all of the 
components of the system and are designed to evaluate the performance of 
multiple receivers used in a differential mode. The field practices and system 
test have to reflect the particular observing strategies (for example, static, 
rapid static, or stop and go) that are employed on a project. The equipment 
should be operated according to the manufacturer's specifications. The test 
consists of a measurement of a small test network and the ongoing analysis of 
production results. 



Measurement of a Small Test Network 



B-24. Control should be established on at least one baseline of the small test 
network. This control consists of a measurement of— 

(n +1) stations and (n +1) independent baselines 

where- 

n = the number of receivers 

B-25. The test network observed should be a polygon with station spacing not 
less than 50 meters and not more than 10 kilometers. The independently 
observed baselines should be processed, baseline by baseline, to produce 
differences in Cartesian coordinates in the satellite datum (AX, AY, and AZ) 
for each baseline. The summation of these differences, for any closed figure, 
will give a preliminary indication of the performance of the total GPS and is 
an initial, minimum field analysis. At the first opportunity, performance of a 
more rigorous approach is essential. The vectors and their associated 
variance-covariance matrices should be adjusted by the least-squares method 
to obtain a more complete and comprehensive report on the equipment test. If 
the results meet the manufacturer's specification, then the manufacturer's 
specification can be adopted by the user as the measure of the precision 
attainable with the system. If not, the user's measurement system must be 
modified to meet the manufacturer's specification or the lower precision must 
be accepted. 



Analysis of Production Results 



B-26. The measurement of a GPS-S network involves the observation of 
closed figures. An analysis of the closure of all figures should be carried out to 
ensure that each figure closes within the expected precision. Closure polygons 
must combine data from different sessions. A network adjustment is the most 
efficient way to confirm agreement with established control at the required 
accuracy. 



B-10 Control-Survey Standards 



FM 3-34.331 



OBSERVATION REQUIREMENTS 



B-27. The observation duration has to be long enough to resolve ambiguities 
and, depending upon the required accuracy, it also has to be long enough to 
average out multipath effects. This is especially true for second-order and 
higher surveys. It is preferred to observe five or more satellites, although most 
techniques will work with a minimum of four satellites. The extra satellites 
give protection against loss of lock from one of the satellites and speeds up the 
ambiguity-resolution process. 

B-28. Equipment users should refer to the manufacturer's specifications for 
DOP. DOP is an indicator of the geometrical strength of a four-or-more 
satellite constellation as it applies to instantaneous point-position fixing. 
PDOP refers to the three position coordinates (while GDOP includes a term 
for the clock offset). The lower the number, the better the geometry for 
achieving an accurate point position. Use caution in applying this parameter 
as an absolute acceptance or rejection criterion, particularly in relative GPS 
positioning where longer observation periods remove most common biases. 
However, sufficiently changing geometry during a recording session assists in 
the determination of ambiguities. Once the ambiguities are resolved, PDOP 
should be kept low. 

B-29. The minimum satellite elevation is 15°. This requirement can be 
reduced to 10° for third-order and lower surveys. It is necessary to ensure that 
the receiver-data rates are the same or a common integer factor of 60", which 
results in sufficient common data to resolve ambiguities. Give special 
attention when processing data collected from different types of receivers (5", 
10", 20", or 30" are typical). The time intervals must also be simultaneous. 

B-30. When a reflective environment (horizontal, vertical, or skew) cannot be 
avoided, refrain from using both low satellites and satellites within half an 
hour either side of culmination for that site. Occupy the position (and the 
others in the same session) for a minimum number of minutes that is equal to 
40 divided by the perpendicular distance to the suspected reflecting surface. 
This will generally increase the chance of capturing at least one full swing of 
the interference. When third-order and higher accuracies are required and a 
site with a reflective environment cannot be avoided, it is worthwhile to 
average longer observation times of the interference (virtually the equivalent 
of a static survey). 

B-31. Manufacturers generally give a guide for the average time required to 
resolve ambiguities. When these times are shorter than the minimum 
observation duration recommended above for reducing multipath, the 
observation duration should be lengthened (following the above guide) if in a 
reflective envi ronment. 

B-32. Field procedures are substantially the same as recommended above 
when using static and kinematic techniques for requirements less stringent 
than second order. This is because relative GPS can routinely deliver second- 
order accuracy. Refer to the manufacturer's manual for any additional 
requirements. RTK carrier-phase techniques already impact on the first 
10 kilometers of second- and lower-order surveys. At this stage of the analysis, 
different criteria should be applied depending on the project requirements. A 
summary of the various observational techniques follow. 



Control-Survey Standards B-11 



FM 3-34.331 



Static 



Rapid Static 



B-33. Static surveying uses two or more receivers that remain stationary for 
30 minutes or more, depending on the line length and the required accuracy. 
Carrier-phase observations are made, and to enhance the carrier-phase 
ambiguity resolution, the satellite geometry should be given time to change. 
Observations are made (with two or more receivers that have a common data 
rate) to four or more satellites with elevations above 15°. An accuracy of 0.1 to 
10 ppm is possible, depending upon the quality of the data, the processing, 
and the length of the baseline vectors. 



B-34. Rapid-static surveying uses various combinations of observations (for 
example, C/A-, P- or Y-code range data and LI and L2 carrier-range data). If 
the view of the sky is limited, rapid-static surveying depends on least-squares 
ambiguity estimation for a determination of the correct ambiguities. The 
reliability is enhanced when data from six or more satellites are used and 
multiple occupations are made at different sidereal times. Dual -frequency 
receivers are advantageous because they allow various data combinations (for 
example, widelaning) in estimating a solution. Occupation times of 2' to 10' is 
required to obtain centimeter-level accuracy for vector lengths up to 
10 kilometers. 



Stop-and-Go Kinematic 



B-35. Stop-and-go-kinematic surveying involves alternately stopping and 
moving of one receiver, with the main interest being in the stopped positions. 
This technique relies upon determining baselines, with a minimum amount of 
data, by resolving the carrier-phase ambiguities at the beginning and 
maintaining lock throughout the survey. 

B-36. I n stop-and-go surveying, two receivers observe a predetermined 
baseline and perform an antenna swap. The antenna swap is used to obtain 
the baseline in a matter of a few minutes. The process where carrier-phase 
ambiguities between satellites and receivers are resolved before the other 
receiver starts roving is called initialization. 

B-37. The second receiver then starts roving, staying stationary over points 
for a few seconds to a few minutes. Constant satellite lock should be 
maintained on at least four satellites and is the major factor with this 
technique, which makes it suitable for open terrain only. An accuracy of 20 to 
30 millimeters is possible, and accuracies of 1 to 10 ppm have been quoted. 
Good geometry and the observation of a minimum of a dozen epochs at each 
survey point are important for this technique. The short occupation times give 
a rapid drop-off in height accuracy. Good planning is advantageous, and the 
occasional occupation of a known point is necessary in case the geometry 
deteriorates or a cycle slip occurs before the survey can be closed. RTK 
methods fit this category, because RTK presupposes access to actual phase 
observations at a site with known coordinates, to produce a double-difference, 
ambiguity-fixed solution in real time. 



B-12 Control-Survey Standards 



FM 3-34.331 



Kinematic 



B-38. Kinematic surveying proceeds as in stop-and-go-kinematic surveying 
but without stopping. Vectors are created that are associated with single 
epochs in time. 



Pseudokinematic 



B-39. Pseudokinematic surveying does not depend on continuous lock of the 
rover(s) while traveling but requires continuous lock while stationary. The 
same point is reoccupied after 1 to 2 hours by the same receiver and again for 
about 3' to 10'. This creates a situation of having one deliberate cycle slip 
dividing the data. This paired observation is defined as a single station 
observation. Obtaining the change in satellite geometry enhances the 
ambiguity resolution. A constant antenna height allows the two data sets to 
represent measurements to the same physical point in space. 

B-40. Accuracies can reach 20 to 30 millimeters depending upon satellite 
availability and PDOP. Accuracies of 2 to 20 ppm have been quoted. Single- or 
dual-frequency carrier-phase receivers can be used. Dual-frequency 
observations, although not necessary, enhance the determination of the 
ambiguities. For practical purposes, maximum vector lengths are about 
15 kilometers. 

B-41. While not as productive as the stop-and-go-kinematic technique, the 
pseudokinematic technique does not rely on maintaining satellite lock. The 
pseudokinematic technique is much more practical in areas where trees, 
buildings, tunnels, overpasses, or other obstructions are likely to interrupt the 
signal or where interstation access is slow. 



OTF/RTK Kinematic 



DGPS 



B-42. OTF/RTK surveying uses a continuous kinematic technique, which is 
ideal when the roving receiver cannot stop for an initialization. OTF/RTK does 
not need initialization; it performs auto-reverse processing as soon as the 
ambiguities are resolved. Contrary to the definition of kinematic techniques, 
OTF/RTK does not need initialization at the start. A sufficient number of 
dual-frequency observations to, preferably, five satellites with good PDOP are 
required. After the dual-frequency observations, only four satellites are 
required. Vectors are created that are associated with single epochs in time. 
For distances up to 20 kilometers, a conventional static or rapid-static setup is 
required as initialization. Single-frequency techniques are also used with 
OTF/RTK. 



B-43. The term differential is generally used with pseudorange techniques 
that resolve the errors in a single position. One of these techniques is real- 
time DGPS, which resolves the errors in real time. This is in contrast to the 
vector approach of relative GPS, which is achieved by observing C/A-code- 
phase (pseudorange) error measurements at one or more known stations and 
then transmitting the data to the remote station(s). 



Control-Survey Standards B-13 



FM 3-34.331 



B-44. TableB-8 shows procedures for static- and kinematic-GPS techniques. 
Occupation time at a point is equipment and distance dependent and is 
sometimes indicated by the receiver. The longer the occupation time the 
greater the chance that ambiguities are resolved and that instrument noise 
and multipath interference is averaged out, which gives more reliability. 

Table B-8. Static and Kinematic GPS 







Procedure 


Technique 


Initiali- 
zation 


Dual/ 

Single 

Frequency 


Common 
Satellites 


Continuous 

Lock 

During 

Travel 


Maximum 
Spacing 


PDOP 5 


Static GPS 


Static 


No 


Optional 


>4 


No 


500 km 


Note 5 


Pseudo- 
kinematic 


No 


Optional 


>4 1 


No, only 
at base 


<20 km 


Note 5 


Rapid static 


No 


Optional 4 


>4 


No 


<10 km 


Note 5 


Kinematic 
GPS 


Kinematic 


Yes 2 


Optional 3 


5 preferred, 
4 possible 


Yes 


<20 km 


<10 


Stop-and-go 


Yes 


Single 


5 preferred, 
4 possible 


Yes 


<20 km 


<10 


OTF/RTK 


No 


Dual or 
single 


5 preferred, 
4 possible 


Preferred, 
but not 
necessary 


<20 km, 

7-10 km 

best 


NA 


1 Four satellites are required in both observation sessions; five or more satellites are an advantage. 

2 Observe a known baseline (at beginning or end) and solve all ambiguities, do an antenna swap, or 
return to the starting point at the end of the survey. 

3 Dual-frequency receivers give an advantage. 

4 Dual-frequency P-code will enhance the speed of the solution. 

Sufficiently changing geometry during a recording session assists in the determination of 
ambiguities, and once they are resolved, PDOP should be kept low. In the kinematic techniques, the 
ambiguities are already resolved through the initialization and the PDOP should be kept low from that 
moment (refer to the manufacturer's specifications). 



REDUCTION AND ANALYSIS PROCEDURES 



B-45. The quality of the results of a GPS-S is determined by both the method 
of observation (including choice of equipment) and the quality of the 
reduction, adjustment, and transformation procedures. The initial station 
position of the datum for any baseline calculation should not exceed 10 meters 
for each ppm accuracy required and is best obtained by transformation or by 
connection toanother point with known coordinates in the satellite datum. 



B-14 Control-Survey Standards 



FM 3-34.331 



B-46. The reduction procedures outlined in Table B-9 give a broad overview of 
the essential components to consider when undertaking the reduction of GPS 
data. Adhering to the procedures in this table does not remove the necessity 
for statistical analysis of the results. The table format gives a clear picture of 
the specific reduction requirements for achieving a given geometric standard 
of survey. These reduction procedures indicate the minimal requirements. 



Table B-9. Recommended Processing Requirements 



Observation 
Distance 


Order and Class 


1st 


2nd, I 


2nd, II 


3rd, I 


3rd, II 


<8 km 


D 1 , DD, FX 


D 1 , DD, FX 


S, DD, FX 


S, DD, FX 


S, DD, FX 


8 to 24 km 


D, DD, FX 


D, DD, FX 


D, DD, FX 


D, DD, FX 


S, DD, FX 


25 to 49 km 


D, DD, 
FX-FT 


D, DD, 
FX-FT 


D, DD, 
FX-FT 


D, DD, FX- 
FT 


D, DD, FX- 
FT 


50 to 90 km 


D, DD,FT 


DDorT 2 , D, 
FT 


DDorT 2 , D, 
FT 


DDorT 2 , D, 
FT 


DDorT 2 , D, 

FT 


90> km 


D, T 


D, T 


D, T 


D, T 


D, T 


1 Use L1 solutions from a dual-frequency receiver to enable ambiguity resolution 
by widelaning. 

2 Double-difference solutions are preferred. Triple-difference solutions are 
increasingly acceptable as the distance increases, and the observation length 
allows sufficient geometry change. 

LEGEND: 

D = dual-frequency receiver 

DD = double-difference solution 

FT = ambiguity-float solution (with repaired cycle slips) 

FX = ambiguity-fixed solution 

S = single-frequency receiver 

T = triple-difference solution 

(with sufficient observation length to allow for a change of geometry) 



B-47. Because of the effect of the ionosphere, dual-frequency receivers are 
used on lines over a certain length. Ll-only solutions often show less noise for 
vector lengths below 10 kilometers. Single-frequency receivers can still satisfy 
high-order survey requirements up to 20 kilometers but need an increasing 
number of hours of observation if a higher order of survey is required or if 
longer baselines are observed. Dual-frequency ambiguity-fixed L1/L2 
solutions in their ion-free linear combination are usually obtained for vector 
lengths from 10 to 50 kilometers. An ambiguity-fixed solution is preferred, but 
as the distance increases, it becomes harder to achieve. Ion-free, ambiguity- 
float L1/L2 solutions have become more common for vectors of 40 to 90 
kilometers. For longer baselines, triple-difference solutions can be used if the 
observation time is long enough to enable a sufficient change in the satellite 



Control-Survey Standards B-15 



FM 3-34.331 



geometry during the recording session. As a guide, use 30 minutes as a 
minimum plus an additional 20 minutes per each 10 kilometers of baseline 
length. 

PROCE SSI NG AND ANALYSI S OF Ml Nl MALLY CONSTRAI NE D ADJ USTME NTS 

B-48. When processing minimally constrained adjustments, the processing 
software must be able to produce the variance/covariance statistics of the 
observed Cartesian vectors so that the adjustments can be input into a 3D 
adjustment program. A least-squares adjustment must be performed when 
deriving values for control surveys. The software must be capable of 
determining transformation parameters between the observed Cartesian 
vectors and the local geodetic system. 

B-49. Error ellipses should be calculated after a minimally constrained least- 
squares adjustment. These calculations prove the quality of the network 
design rather than the quality of the observations. The error ellipses should 
be scaled by the a priori variance of unit weight (generally equal to one), 
unless the a posteriori estimate of variance does not pass the chi-square test. 
I n the latter case, the observations, the statistical model, or even the 
mathematical model should be examined and the problem remedied and the 
adjustment rerun. I n the case of not being able to remedy the situation, the 
error ellipses should be scaled by the a posteriori variance factor. 

B-50. To confirm the quality of the observations, the standardized residuals 
should be checked for outliers. The checking of the statistics often involves 
critical evaluation of the a priori standard deviations of the observations. If 
the baseline variance/covariance matrix is routinely modified by a multiplier, 
documentation of a measurement over a test network may be required as 
confirmation of the multiplier used. 

B-51. To conform to the internal consistency requirements for a particular 
geometric accuracy, the error ellipses should confirm the capability of the 
network design to meet the specifications. The standardized residuals and the 
estimate of variance should confirm that the observations have actually met 
the required standard. 

B-52. All points in a survey should conform to the specifications belonging to 
the relevant classification. This applies whether the points are connected by 
baseline observations or not. This is also valid when relative accuracy values 
are calculated to points with previously established coordinate values. Geoid- 
separation values are applied to orthometric heights of points that will be 
constrained in the transformation and adjustment. 

DERIVATION OF GEOI D-SEPARATION VALUES 

B-53. The foil owing four methods are used for determining geoid heights: 

• Geodetic-leveling-geoid method. The use of a geodetic-leveling 
geoid. 

• Global-geopotential-model method. The use of different types of 
global-geopotential models derived from gravity and active or passive 
satellite information. 



B-16 Control-Survey Standards 



FM 3-34.331 



• Gravimetric method. The use of an intensive grid of local gravity, 
together with a high-degree global-geopotential model. 

• Geometrically modeled geoid method. The use of a geometrically 
modeled geoid by contouring geoid-height values derived from 
orthometricand ellipsoidal heights. 

B-54. The relative accuracy of height values resulting from the global- 
geopotential-model method are dependent on the grid spacing of the 
geopotential model used. The spacing of points with observed local gravity in 
the gravimetric method and the spacing of leveled points in the geometrically 
modeled geoid method determine the relative accuracy. 

B-55. Thegeodetic-leveling-geoid method is generally not accurate enough to 
convert G PS-ellipsoidal heights intoorthometric heights but works well with 
height differences. Theglobal-geopotential-model method is useful in the case 
of long baselines in an area with a smooth geoid and scarce orthometric-height 
points. The gravimetric method is the most accurate when a sufficient dense 
grid of gravity information is available. The geometrically modeled geoid 
method is the most accurate when sufficient orthometric information is 
available. When orthometric information is scarce and the geoid is not 
smooth, surface fitting and contouring are not recommended for short 
distances (10 kilometers or less). 

TRANSFORMATION AND CONSTRAINED ADJ USTMENTS 

B-56. The next step is the derivation of transformation parameters between 
the minimally constrained adjusted vectors and the selected constrained 
points in the local geodetic system. This is usually carried out together with a 
constrained least-squares adjustment. This adjustment is subjected to the 
same analysis as the minimally constrained adjustment. Error ellipses are 
calculated again and the network is allocated an accuracy order that enables 
its orderly integration with the database that contains the existing data set of 
established coordinates. 

NOTE: Refer to E M 1110-1-1003 for a complete sample of an 
adjustment statistics summary. 



Control-Survey Standards B-17 



Appendix B 

Control-Survey Standards 

This appendix is designed as a quick reference for platoon leaders. It 
summarizes the standards for control surveys that were discussed in 
Chapters 6, 7, and 8. 

DIFFERENTIAL LEVELING 

B-l. Differential leveling is the conventional method of leveling for the 
propagation of orthometric heights. TableB-1 and Tables B-2 and B-3, 
pages B-2 and B-3, show the overall standards and specifications for 
differential leveling. 

TableB-1. Equipment Standards 



Requirement 


Order and Class 


1st, I 


1st, II 


2nd, I 


2nd, II 


3rd 


Level 


0.2 mm/km 
spirit level 


0.4 mm/km 
electronic bar 
code 


Automatic level 
with parallel- 
plate 

micrometer or 
0.4 mm/km 
electronic bar 
code 


0.8 mm/km 
automatic level 
with parallel- 
plate micrometer 
or electronic bar 
code 


3-wire 

automatic 

level 


Staff construction 


Rigid invar 


Rigid invar 


Rigid invar 


Rigid invar 


Wood or 
metal 


Staff graduation interval (mm) 


5 


5 


5 or 10 


5 or 10 


10 


Tripod construction 


Rigid 


Rigid 


Rigid 


Rigid 


Rigid 


Bubble attached to staff 


Yes 


Yes 


Yes 


Yes 


Yes 


Solid, portable change points 


No 


No (route is 
premarked) 


Yes 


Yes 


Yes 


Umbrella for level 


Yes 


Yes 


Yes 


Yes 


No 



Control-Survey Standards B-1 



FM 3-34.331 







Table B-2. 


Equipment Testing 






Requirement 


Order and Class 


1st, I 


1st, II 


2nd, I 


2nd, II 


3rd 


System test before 
commencement 


Yes 


Yes 


Yes 


Yes 


Optional 


Maximum standard error in the 
line of sight (mm/m) 


0.05 


0.05 


0.05 


0.05 


0.1 


Vertical 

collimation 

check 


Frequency 


Daily 


Daily 


Daily 


Daily 


Daily 


Maximum 
collimation error 
(mm/m) 


0.02 


0.02 


0.02 


0.02 


0.04 


Level cross-hair verticality check 


Yes 


Yes 


Yes 


Yes 


Yes 


Staff calibration standard 


N 


N 


N 


M 


M 


Time between calibration (years) 


1 


1 


NA 


NA 


NA 


Staff bubble verticality to be within 


10' 


10' 


10' 


10' 


10' 


LEGEND: 

M = Manufacturer's standard 
N = National standard 



B-2 Control-Survey Standards 



FM 3-34.331 



Table B-3 


. Observation and Reduction Requirements 




Requirement 


Order and Class 


1st, I 


1st, II 


2nd, 1 


2nd, II 


3rd 


Instrument leveled by an 
unsystematic method 


Yes 


Yes 


Yes 


Yes 


Yes 


Leap-frog system of progression 
used 


Yes 


Yes 


Yes 


Yes 


Yes 


Staff readings recorded to nearest 
(mm) 


0.01 


0.01 


0.1 


0.1 


1 


Temperature recorded 


Start, 

middle, 

finish 


Start, 

middle, 

finish 


At start and finish of each leveling run and 
at pronounced changes of temperature 


Maximum length of sight (m) 


50 


60 


60 


70 


90 


Minimum ground clearance of line 
of sight (m) 


0.5 


0.5 


0.5 


0.5 


0.5 


Backsight and foresight lengths to 
be equal within (m) 


2 


5 


5 


10 


10 


Observation time 


Before 
1000 and 
after 1400 


Before 
1000 and 
after 1400 


Before 1 000 
and after 
1400 


Any time, provided 
atmospheric conditions allow 
positive resolution of staff 
graduation 


Two-way leveling 


Yes 


Yes 


Yes 


Yes 


Yes 


Even number of instrument setups 
between BMs 


Yes 


Yes 


Yes 


Yes 


Yes 


Maximum section misclosure 
(mm) 


37km 


47km 


67km 


87km 


127km 


Maximum loop misclosure (mm) 


47km 


57km 


67km 


87km 


127km 


Minimum number of BMs 


3 


3 


3 


3 


3 


Double-leveled BM 


Yes 


Yes 


Yes 


Yes 


Yes 


Maximum BM misclosure (mm) 


47km 


57km 


67km 


87km 


127km 


Orthometric correction 
(collimation) to be applied 


Yes 


Yes 


Yes 


Yes 


Yes 



HORIZONTAL-ANGLE MEASUREMENT 



B-2. The observation requirements for horizontal-angle measurements are 
shown in TableB-4, pageB-4. Adherence to these requirements should ensure 
that the appropriate level of precision is achieved. 



Control-Survey Standards B-3 



FM 3-34.331 



Table B-4. Observation Requirements 











Order and Class 




1st 


2nd, I 


2nd, II 


3rd 


3rd, II 


Required 
time of day 


2 hours either side of sunrise/set 
Any time except 1 200 to 1 500 
Any time (subject to checks) 


Yes 
NA 
NA 


Yes 
NA 
NA 


NA 
Yes 
NA 


NA 
NA 
Yes 


NA 
NA 
NA 


Instrument least count 


0.2" 


0.2" 


1.0" 


1.0" 


1.0" 


Horizontal zero settings 


0.2" theodolite 
1" theodolite 


Yes 
NA 


Yes 
Yes 


NA 
Yes 


NA 
Yes 


NA 
Yes 


Sets 


Minimum number of positions (horizontal) 
Number observations (vertical) 


16 
3 


16 
3 


8 1 /12 2 
2 


4 
2 


2 
2 


Field 
checks 


Horizontal 


Ranges between each set: 
standard deviation of mean 
should never exceed 


0.4" 


0.5" 


0.8" 


1.2" 


2.0" 


Ranges within each set: 
standard deviation of mean 
should never exceed 


4" 


4" 


5" 


5" 


5" 


Vertical 


Number of observations 
Maximum spread 


3 

10" 


3 

10" 


2 

10" 


2 

10" 


2 

20" 


Infrared 
distance 


Number of observations 


10 


10 


10 


10 


10 


Minimum number of network control points 


4 


3 


2 


2 


2 


Azimuth closure (arc seconds) 


1.7 JR 


37N 


4.57N 


io7n 


127N 


Closure ratio 


1:100,000 


1:50,000 


1:20,000 


1:10,000 


1:5,000 


Position closure 


0.047km 


0.087km 


0.20 7km 


0.40 7km 


0.80 7km 


1 lf using a 0.2" theodolite. 
2 lf using a1" theodolite. 

LEGEND: 

N = number of stations 



TRIGONOMETRIC OBSERVATIONS 



B-3. Trigonometric observations are used to determine trigonometric 
elevations. To achieve a desired order of trigonometrical elevation, use the 
procedures and standards for the particular observation type (for example, 
vertical angle or distance) unless specified otherwise in TableB-5. 



B-4 Control-Survey Standards 



FM 3-34.331 





Table B-5. 


Observation Requirements 




Requirement 


Order 


1st 


2nd 


3rd 


Simultaneous reciprocal 


Yes 


Yes 


Optional 


Nonsimultaneous reciprocal 


NA 


Yes 


Optional 


One-way observation 


NA 


NA 


Yes 


Observation time 


>16 km 


1400 to 1600 


1400 to 1600 


1400 to 1600 


<16 km 


1000 to 1600 


1000 to 1600 


1000 to 1600 


Number of sets 


2 


2 


1 


Number of pointings (per set) 


6 


6 


6 


Maximum range per set (in) 


6 


6 


8 


Meteorological observation 


Yes 


Yes 


Yes 



GPSTECHNIQUES 



B-4. There are two fundamental GPS techniques— relative and absolute- point 
positioning. The recommended practices for the GPS refer only to relative 
positioning. Relative positioning requires two or more GPS receivers. The two 
fundamental types of GPS receivers are navigational and survey (or geodetic). 
The receivers are distinguished by the accuracy level and type of 
measurements taken during surveys. Many receivers are capable of a number 
of measurement types. Pseudorange and carrier-phase measurements are the 
two fundamental types of measurements made with GPS receivers. 



RELATIVE-POSITIONING TECHNIQUES 



B-5. Relative-positioning techniques can be divided into two main groups- 
static and kinematic. The fundamental difference is that kinematic 
techniques require maintaining lock throughout the survey after ambiguity 
resolution. These static and kinematic techniques employ carrier-phase 
measurements. Since a carrier-beat-phase measurement is the only type that 
offers a sufficient precision in geodetic positioning at third order and higher, 
the use of receivers that measure the carrier phase is mandatory. Static and 
kinematic techniques can be grouped as follows: 

• The static group can be divided into the following techniques: 

Static (also referred to as classic static). 

Pseudokinematic (for example, intermittent static, pseudostatic, 

or reoccupation kinematic). 

Rapid static (also referred to as quick static or fast static). 

• The kinematic group can bedivided into the following techniques: 

Stop-and-go kinematic (also referred to as intermittent kinematic 

or semi kinematic). 

Kinematic (also referred to as continuous kinematic). 

OTF/ (also referred to as ambiguity-resolution OTF). 

B-6. A third group of relative-positioning techniques is based on pseudorange 
measurements. These techniques, either in postprocessed or real-time modes, 



Control-Survey Standards B-5 



FM 3-34.331 



are referred to as DGPS and aregenerally not used for precise control surveys. 
DGPS is used for accuracies of 2 to 5 meters. Precise DGPS is used for 
accuracies of 1 meter or less. 

B-7. By combining carrier-phase measurements with pseudorange 
measurements, it is possible to reach higher accuracies with DGPS 
techniques. While GPS measurements are receiver dependent, the selection of 
observation techniques is dependent on the precision required and the 
reduction process to be used. 



NETWORK DESIGN AND GEOMETRY 



B-8. When planning a GPS-S, the first step is to choose the appropriate 
technique for the precision required. TableB-6 provides a guide for what 
technique to use to achieve a particular order and class of survey. TableB-7 
provides references to the order and class of survey. 

Table B-6. Positioning Techniques 



Technique 


Order and Class 


1st 


2nd, I 


2nd, II 


3rd 


Static 


Yes 


Yes 


Yes 


Yes 


Rapid static 


NA 


NA 


Yes 


Yes 


Pseudokinematic 


NA 


NA 


NA 


Yes 


Stop and go 


NA 


NA 


NA 


Yes 



B-9. The location and distribution of points in a GPS-S do not depend 
significantly on factors such as network shape or intervisibility but rather on 
an optimum layout with sufficient redundancy for carrying out the intent of 
the survey. The intent of the network design should be to— 

• Locate new points so that the line of sight between them is clear 
(when possible). 

• Provide error control in the minimum-constraint solution (to enable 
data validation) and analysis of the accuracy of the survey. 

• Producetie-offs for integrating the survey into previously established 
control . 

• Locate ties to points with existing orthometric heights. 

B-10. Redundancies play an important role in fulfilling this intention. All 
GPS-Ss must be connected to theexisting control, theNGS, or the local project 
to ensure survey integration, legal tractability, and quality assurance. If 
established control stations are not available in the vicinity of the survey, 
bring control to the appropriate accuracy by using GPS or conventional 
techniques. When selecting established stations to connect to, give preference 
to the highest order of the nearest, established permanent marks (or geodetic 
stations) that are easily accessible. Connection should be made to a minimum 
of three points with suitable MSL heights, preferably enclosing the survey, 
and a minimum of two points with established (horizontal) coordinates. 
Additional points are to be connected to obtain quality control, with preference 



B-6 Control-Survey Standards 



FM 3-34.331 



Table B-7. Positioning References 



Reference 


Order and Class 


1st 


2nd, I 


2nd, II 


3rd 


Minimum station spacing 1 (km) 


5 


1 


0.5 


0.2 


Typical station spacing 2 (km) 


100-500 


10-100 


0.5-10 


0.1-5 


Independent 
occupations 
per station 3 


at least 3 times 
(% of total stations) 


50% 


40% 


20% 


10% 


at least 2 times 
(% of total stations) 


100% 


100% 


100% 


100% 


Minimum common satellites 


4 satellites 


Minimum PDOP required 


Less than 10 after resolution of ambiguities 


Minimum satellite elevation 


15° 


Data rate 


Optional 


Minimum observation period (static) 4 


120' 


60' 


45' 


30' 


Minimum independent baselines at 
each station 


3 


3 


2 


2 


1 The values relate to the use of conventional equipment and proprietary software. 

independent occupations per station may be back to back, but the antenna should 
be reset for each occupation. Antenna heights are to be changed by at least 0.1 to 
0.2 meter unless set up on a pillar. The fully specified minimum-observation time 

should be met with each occupation. 

3 For example, for a second-order, Class II network, aim for 20 percent of stations to 

be occupied at least three times and 100 percent of stations to be occupied at least 

twice. 

4 As a rule, 30 minutes as a definitive minimum plus about 2 minutes per kilometer. 



given to coordinated marks that enclose the surveyed area and height points 
spaced throughout the area. A least-squares adjustment of the control survey 
must be performed. 

B-ll. The planning of the observations should be such that the error budget is 
sufficiently minimized. Consider the error budget of a double difference, which 
consists of error sources affecting measurements; error sources that depend 
upon the site and the type of instrumentation used; and error sources 
resulting from reduction, adjustment, and transformation. 

B-12. Error sources that affect measurements are tropospheric refraction, 
ionospheric refraction, and orbit errors. The main error sources affected by the 
site's location and the instrumentation are centering and antenna-height 
accuracy, antenna-phase center variation, 3D differential -antenna offset, 
multipath and imaging errors, differential tropospheric delay, and differential 



Control-Survey Standards B-7 



FM 3-34.331 



ionospheric delay when using single-frequency solutions. The main error 
sources resulting from reduction, adjustment, and transformation are the 
selection of the wrong ambiguities, insufficient redundancy for quality control 
of the transformation solution, and a geoid model that is too simple or based 
on too sparse data. 



REDUNDANCY 



B-13. Redundancy in the observations is the best way of dealing with most of 
the error sources. Specific observing procedures and differencing techniques 
can eliminate other error sources that are more systematic. Error sources are 
reduced by careful site selection, averaging, and sufficient observation time to 
allow geometry change. Night observations or the use of dual-frequency 
receivers can minimize ionospheric errors. Antenna offset can be minimized 
by ensuring identical antenna orientations. Orbit errors are minimized by the 
use of precise ephemerides. 

B-14. The concept of redundancy (when using a GPS) refers to such things as 
the following: 

Increasing the percentage of points with multiple occupations. 

Tying multiple baselines into one point. 

Observing common baselines between figures. 

Closing onto existing control. 

Computing the polygon closure using data derived from different 

sessions. 

Observing morethan the minimum number of satellites. 

Averaging through observing a sufficient number of epochs. 

B-15. I ndependent reoccupation of the same point (after a sufficient lapse of 
time) to observe a different baseline is the most common way of detecting 
gross error. An alternative to independent reoccupations is the inclusion of 
conventional observations of appropriate accuracy (for example, to create ties 
between unclosed GPS polygons in the same adjustment). I n a control survey, 
all observations should be checked by the redundancies included in the 
network. The configuration of the network should involve the observation of 
closed figures, and closure polygons must combine data from different 
sessions. 



INDEPENDENT BASELINES 



B-16. An independent-baseline measurement in an observation session is 
achieved when the data used are not just different combinations of the same 
data used in computation of other baseline vectors observed in that session. In 
an observation session using five receivers, the total number of baselines can 
be computed as follows: 

Total number of baselines = = = 10 

where— 

n = the number of receivers 



B-8 Control-Survey Standards 



FM 3-34.331 



B-17. However, only four (n - 1) of those baselines are independent. The 
remainders (10 -4=6) are formed from combinations of phase data used to 
compute the independent baselines. The results from observations of the same 
baseline made in two different sessions are independent. Generally, 
independent-baseline processors assume that there is no correlation between 
independent vectors. Trivial baselines may be included in the adjustment to 
makeupfor such a deficient statistical model. If the mathematical correlation 
between two or more simultaneously observed vectors in a session is not 
carried in the variance-covariance matrix, the trivial baselines take on a 
bracing function that simulates the effect of the proper correlation statistics. 
And, at the same time, introduce a false redundancy in the count of the 
degrees of freedom. I n this case, the number of trivial baselines in an 
adjustment should be subtracted from the number of redundancies before the 
variance factor (variance of unit weight) is calculated. If this approach is not 
followed, trivial baselines will be excluded from the network altogether. 



INCORPORATION OF GPS SURVEYS 



B-18. To incorporate 3D GPS-Ss into local horizontal and vertical data 
(WGS-84 and MSL), the number, type, and distribution of control points to 
which connections should be made must be considered. A determination of 
which technique to use to derive orthometric heights from ellipsoidal heights 
is necessary. The technique will influence the choice of well-placed strategic 
points with known orthometric heights that should be observed. Alternatively, 
orthometric heights can be brought to selected points in the GPS network. 

B-19. For a small area (a few kilometers across) with a smooth geoid, solving 
for transformation parameters brings about a de facto surface fit (tilting the 
ellipsoid so that it is parallel with the geoid). When a single value for the 
geoid-spheroid separation is used at the orthometric-control points, it is 
assumed that the geoid is as smooth as the ellipsoid. For larger areas, choose 
between a geodetic-leveling, a geopotential model-based, a gravimetric, or a 
geometrically derived geoid. 

B-20. The classification of GPS results (including height) is generally 
expressed using a linear propagation method, unless requirements specifically 
call for height classification using differential leveling. I n both cases, the class 
and the order are assigned separately for horizontal and vertical control. 



SYSTEM TESTING 



B-21. A system test is recommended to qualify equipment, techniques, and 
error modeling for a particular accuracy. Evidence of a test may be required 
after acquisition of new equipment or software, when trying new techniques, 
or as justification of a chosen method of error modeling. This evidence 
serves— 

• As a justification of observing and processing techniques. 

• To validate (under similar conditions) the same equipment, the 
software, and the observation method. 

• Tojustify the error modeling. 

• As a justification of a multiplier used to increase the baseline-vector 
variance-covariance matrix elements when these are unrealistic. 

• To validate data when combining results from different equipment 
and software. 



Control-Survey Standards B-9 



FM 3-34.331 



B-22. The total GPS process is comprised of the following four distinct 
components: 

• Satellites. 

• Receiver hardware. 
Field procedures. 

• Software. 

B-23. The following procedures describe a system test that considers all of the 
components of the system and are designed to evaluate the performance of 
multiple receivers used in a differential mode. The field practices and system 
test have to reflect the particular observing strategies (for example, static, 
rapid static, or stop and go) that are employed on a project. The equipment 
should be operated according to the manufacturer's specifications. The test 
consists of a measurement of a small test network and the ongoing analysis of 
production results. 



Measurement of a Small Test Network 



B-24. Control should be established on at least one baseline of the small test 
network. This control consists of a measurement of— 

(n +1) stations and (n +1) independent baselines 

where- 

n = the number of receivers 

B-25. The test network observed should be a polygon with station spacing not 
less than 50 meters and not more than 10 kilometers. The independently 
observed baselines should be processed, baseline by baseline, to produce 
differences in Cartesian coordinates in the satellite datum (AX, AY, and AZ) 
for each baseline. The summation of these differences, for any closed figure, 
will give a preliminary indication of the performance of the total GPS and is 
an initial, minimum field analysis. At the first opportunity, performance of a 
more rigorous approach is essential. The vectors and their associated 
variance-covariance matrices should be adjusted by the least-squares method 
to obtain a more complete and comprehensive report on the equipment test. If 
the results meet the manufacturer's specification, then the manufacturer's 
specification can be adopted by the user as the measure of the precision 
attainable with the system. If not, the user's measurement system must be 
modified to meet the manufacturer's specification or the lower precision must 
be accepted. 



Analysis of Production Results 



B-26. The measurement of a GPS-S network involves the observation of 
closed figures. An analysis of the closure of all figures should be carried out to 
ensure that each figure closes within the expected precision. Closure polygons 
must combine data from different sessions. A network adjustment is the most 
efficient way to confirm agreement with established control at the required 
accuracy. 



B-10 Control-Survey Standards 



FM 3-34.331 



OBSERVATION REQUIREMENTS 



B-27. The observation duration has to be long enough to resolve ambiguities 
and, depending upon the required accuracy, it also has to be long enough to 
average out multipath effects. This is especially true for second-order and 
higher surveys. It is preferred to observe five or more satellites, although most 
techniques will work with a minimum of four satellites. The extra satellites 
give protection against loss of lock from one of the satellites and speeds up the 
ambiguity-resolution process. 

B-28. Equipment users should refer to the manufacturer's specifications for 
DOP. DOP is an indicator of the geometrical strength of a four-or-more 
satellite constellation as it applies to instantaneous point-position fixing. 
PDOP refers to the three position coordinates (while GDOP includes a term 
for the clock offset). The lower the number, the better the geometry for 
achieving an accurate point position. Use caution in applying this parameter 
as an absolute acceptance or rejection criterion, particularly in relative GPS 
positioning where longer observation periods remove most common biases. 
However, sufficiently changing geometry during a recording session assists in 
the determination of ambiguities. Once the ambiguities are resolved, PDOP 
should be kept low. 

B-29. The minimum satellite elevation is 15°. This requirement can be 
reduced to 10° for third-order and lower surveys. It is necessary to ensure that 
the receiver-data rates are the same or a common integer factor of 60", which 
results in sufficient common data to resolve ambiguities. Give special 
attention when processing data collected from different types of receivers (5", 
10", 20", or 30" are typical). The time intervals must also be simultaneous. 

B-30. When a reflective environment (horizontal, vertical, or skew) cannot be 
avoided, refrain from using both low satellites and satellites within half an 
hour either side of culmination for that site. Occupy the position (and the 
others in the same session) for a minimum number of minutes that is equal to 
40 divided by the perpendicular distance to the suspected reflecting surface. 
This will generally increase the chance of capturing at least one full swing of 
the interference. When third-order and higher accuracies are required and a 
site with a reflective environment cannot be avoided, it is worthwhile to 
average longer observation times of the interference (virtually the equivalent 
of a static survey). 

B-31. Manufacturers generally give a guide for the average time required to 
resolve ambiguities. When these times are shorter than the minimum 
observation duration recommended above for reducing multipath, the 
observation duration should be lengthened (following the above guide) if in a 
reflective envi ronment. 

B-32. Field procedures are substantially the same as recommended above 
when using static and kinematic techniques for requirements less stringent 
than second order. This is because relative GPS can routinely deliver second- 
order accuracy. Refer to the manufacturer's manual for any additional 
requirements. Real-time-kinematic carrier-phase techniques already impact 
on the first 10 kilometers of second- and lower-order surveys. At this stage of 
the analysis, different criteria should be applied depending on the project 
requirements. A summary of the various observational techniques follow. 



Control-Survey Standards B-11 



FM 3-34.331 



Static 



Rapid Static 



B-33. Static surveying uses two or more receivers that remain stationary for 
30 minutes or more, depending on the line length and the required accuracy. 
Carrier-phase observations are made, and to enhance the carrier-phase 
ambiguity resolution, the satellite geometry should be given time to change. 
Observations are made (with two or more receivers that have a common data 
rate) to four or more satellites with elevations above 15°. An accuracy of 0.1 to 
10 ppm is possible, depending upon the quality of the data, the processing, 
and the length of the baseline vectors. 



B-34. Rapid-static surveying uses various combinations of observations (for 
example, C/A-, P- or Y-code range data and LI and L2 carrier-range data). If 
the view of the sky is limited, rapid-static surveying depends on least-squares 
ambiguity estimation for a determination of the correct ambiguities. The 
reliability is enhanced when data from six or more satellites are used and 
multiple occupations are made at different sidereal times. Dual -frequency 
receivers are advantageous because they allow various data combinations (for 
example, widelaning) in estimating a solution. Occupation times of 2' to 10' is 
required to obtain centimeter-level accuracy for vector lengths up to 
10 kilometers. 



Stop-and-Go Kinematic 



B-35. Stop-and-go-kinematic surveying involves alternately stopping and 
moving of one receiver, with the main interest being in the stopped positions. 
This technique relies upon determining baselines, with a minimum amount of 
data, by resolving the carrier-phase ambiguities at the beginning and 
maintaining lock throughout the survey. 

B-36. I n stop-and-go surveying, two receivers observe a predetermined 
baseline and perform an antenna swap. The antenna swap is used to obtain 
the baseline in a matter of a few minutes. The process where carrier-phase 
ambiguities between satellites and receivers are resolved before the other 
receiver starts roving is called initialization. 

B-37. The second receiver then starts roving, staying stationary over points 
for a few seconds to a few minutes. Constant satellite lock should be 
maintained on at least four satellites and is the major factor with this 
technique, which makes it suitable for open terrain only. An accuracy of 20 to 
30 millimeters is possible, and accuracies of 1 to 10 ppm have been quoted. 
Good geometry and the observation of a minimum of a dozen epochs at each 
survey point are important for this technique. The short occupation times give 
a rapid drop-off in height accuracy. Good planning is advantageous, and the 
occasional occupation of a known point is necessary in case the geometry 
deteriorates or a cycle slip occurs before the survey can be closed. RTK 
methods fit this category, because RTK presupposes access to actual phase 
observations at a site with known coordinates, to produce a double-difference, 
ambiguity-fixed solution in real time. 



B-12 Control-Survey Standards 



FM 3-34.331 



Kinematic 



B-38. Kinematic surveying proceeds as in stop-and-go-kinematic surveying 
but without stopping. Vectors are created that are associated with single 
epochs in time. 



Pseudokinematic 



B-39. Pseudokinematic surveying does not depend on continuous lock of the 
rover(s) while traveling but requires continuous lock while stationary. The 
same point is reoccupied after 1 to 2 hours by the same receiver and again for 
about 3' to 10'. This creates a situation of having one deliberate cycle slip 
dividing the data. This paired observation is defined as a single station 
observation. Obtaining the change in satellite geometry enhances the 
ambiguity resolution. A constant antenna height allows the two data sets to 
represent measurements to the same physical point in space. 

B-40. Accuracies can reach 20 to 30 millimeters depending upon satellite 
availability and PDOP. Accuracies of 2 to 20 ppm have been quoted. Single- or 
dual-frequency carrier-phase receivers can be used. Dual-frequency 
observations, although not necessary, enhance the determination of the 
ambiguities. For practical purposes, maximum vector lengths are about 
15 kilometers. 

B-41. While not as productive as the stop-and-go-kinematic technique, the 
pseudokinematic technique does not rely on maintaining satellite lock. The 
pseudokinematic technique is much more practical in areas where trees, 
buildings, tunnels, overpasses, or other obstructions are likely to interrupt the 
signal or where interstation access is slow. 



OTF/RTK Kinematic 



DGPS 



B-42. OTF/RTK surveying uses a continuous kinematic technique, which is 
ideal when the roving receiver cannot stop for an initialization. OTF/RTK does 
not need initialization; it performs auto-reverse processing as soon as the 
ambiguities are resolved. Contrary to the definition of kinematic techniques, 
OTF/RTK does not need initialization at the start. A sufficient number of 
dual-frequency observations to, preferably, five satellites with good PDOP are 
required. After the dual-frequency observations, only four satellites are 
required. Vectors are created that are associated with single epochs in time. 
For distances up to 20 kilometers, a conventional static or rapid-static setup is 
required as initialization. Single-frequency techniques are also used with 
OTF/RTK. 



B-43. The term differential is generally used with pseudorange techniques 
that resolve the errors in a single position. One of these techniques is real- 
time DGPS, which resolves the errors in real time. This is in contrast to the 
vector approach of relative GPS, which is achieved by observing C/A-code- 
phase (pseudorange) error measurements at one or more known stations and 
then transmitting the data to the remote station(s). 



Control-Survey Standards B-13 



FM 3-34.331 



B-44. TableB-8 shows procedures for static- and kinematic-GPS techniques. 
Occupation time at a point is equipment and distance dependent and is 
sometimes indicated by the receiver. The longer the occupation time the 
greater the chance that ambiguities are resolved and that instrument noise 
and multipath interference is averaged out, which gives more reliability. 

Table B-8. Static and Kinematic GPS 







Procedure 


Technique 


Initiali- 
zation 


Dual/ 

Single 

Frequency 


Common 
Satellites 


Continuous 

Lock 

During 

Travel 


Maximum 
Spacing 


PDOP 5 


Static GPS 


Static 


No 


Optional 


>4 


No 


500 km 


Note 5 


Pseudo- 
kinematic 


No 


Optional 


>4 1 


No, only 
at base 


<20 km 


Note 5 


Rapid static 


No 


Optional 4 


>4 


No 


<10 km 


Note 5 


Kinematic 
GPS 


Kinematic 


Yes 2 


Optional 3 


5 preferred, 
4 possible 


Yes 


<20 km 


<10 


Stop-and-go 


Yes 


Single 


5 preferred, 
4 possible 


Yes 


<20 km 


<10 


OTF/RTK 


No 


Dual or 
single 


5 preferred, 
4 possible 


Preferred, 
but not 
necessary 


<20 km, 

7-10 km 

best 


NA 


1 Four satellites are required in both observation sessions; five or more satellites are an advantage. 

2 Observe a known baseline (at beginning or end) and solve all ambiguities, do an antenna swap, or 
return to the starting point at the end of the survey. 

3 Dual-frequency receivers give an advantage. 

4 Dual-frequency P-code will enhance the speed of the solution. 

Sufficiently changing geometry during a recording session assists in the determination of 
ambiguities, and once they are resolved, PDOP should be kept low. In the kinematic techniques, the 
ambiguities are already resolved through the initialization and the PDOP should be kept low from that 
moment (refer to the manufacturer's specifications). 



REDUCTION AND ANALYSIS PROCEDURES 



B-45. The quality of the results of a GPS-S is determined by both the method 
of observation (including choice of equipment) and the quality of the 
reduction, adjustment, and transformation procedures. The initial station 
position of the datum for any baseline calculation should not exceed 10 meters 
for each ppm accuracy required and is best obtained by transformation or by 
connection toanother point with known coordinates in the satellite datum. 



B-14 Control-Survey Standards 



FM 3-34.331 



B-46. The reduction procedures outlined in Table B-9 give a broad overview of 
the essential components to consider when undertaking the reduction of GPS 
data. Adhering to the procedures in this table does not remove the necessity 
for statistical analysis of the results. The table format gives a clear picture of 
the specific reduction requirements for achieving a given geometric standard 
of survey. These reduction procedures indicate the minimal requirements. 



Table B-9. Recommended Processing Requirements 



Observation 
Distance 


Order and Class 


1st 


2nd, I 


2nd, II 


3rd, I 


3rd, II 


<8 km 


D 1 , DD, FX 


D 1 , DD, FX 


S, DD, FX 


S, DD, FX 


S, DD, FX 


8 to 24 km 


D, DD, FX 


D, DD, FX 


D, DD, FX 


D, DD, FX 


S, DD, FX 


25 to 49 km 


D, DD, 
FX-FT 


D, DD, 
FX-FT 


D, DD, 
FX-FT 


D, DD, FX- 
FT 


D, DD, FX- 
FT 


50 to 90 km 


D, DD,FT 


DDorT 2 , D, 
FT 


DDorT 2 , D, 
FT 


DDorT 2 , D, 
FT 


DDorT 2 , D, 

FT 


90> km 


D, T 


D, T 


D, T 


D, T 


D, T 


1 Use L1 solutions from a dual-frequency receiver to enable ambiguity resolution 
by widelaning. 

2 Double-difference solutions are preferred. Triple-difference solutions are 
increasingly acceptable as the distance increases, and the observation length 
allows sufficient geometry change. 

LEGEND: 

D = dual-frequency receiver 

DD = double-difference solution 

FT = ambiguity-float solution (with repaired cycle slips) 

FX = ambiguity-fixed solution 

S = single-frequency receiver 

T = triple-difference solution 

(with sufficient observation length to allow for a change of geometry) 



B-47. Because of the effect of the ionosphere, dual-frequency receivers are 
used on lines over a certain length. Ll-only solutions often show less noise for 
vector lengths below 10 kilometers. Single-frequency receivers can still satisfy 
high-order survey requirements up to 20 kilometers but need an increasing 
number of hours of observation if a higher order of survey is required or if 
longer baselines are observed. Dual-frequency ambiguity-fixed L1/L2 
solutions in their ion-free linear combination are usually obtained for vector 
lengths from 10 to 50 kilometers. An ambiguity-fixed solution is preferred, but 
as the distance increases, it becomes harder to achieve. Ion-free, ambiguity- 
float L1/L2 solutions have become more common for vectors of 40 to 90 
kilometers. For longer baselines, triple-difference solutions can be used if the 
observation time is long enough to enable a sufficient change in the satellite 



Control-Survey Standards B-15 



FM 3-34.331 



geometry during the recording session. As a guide, use 30 minutes as a 
minimum plus an additional 20 minutes per each 10 kilometers of baseline 
length. 

PROCE SSI NG AND ANALYSI S OF Ml Nl MALLY CONSTRAI NE D ADJ USTME NTS 

B-48. When processing minimally constrained adjustments, the processing 
software must be able to produce the variance/covariance statistics of the 
observed Cartesian vectors so that the adjustments can be input into a 3D 
adjustment program. A least-squares adjustment must be performed when 
deriving values for control surveys. The software must be capable of 
determining transformation parameters between the observed Cartesian 
vectors and the local geodetic system. 

B-49. Error ellipses should be calculated after a minimally constrained least- 
squares adjustment. These calculations prove the quality of the network 
design rather than the quality of the observations. The error ellipses should 
be scaled by the a priori variance of unit weight (generally equal to one), 
unless the a posteriori estimate of variance does not pass the chi-square test. 
I n the latter case, the observations, the statistical model, or even the 
mathematical model should be examined and the problem remedied and the 
adjustment rerun. I n the case of not being able to remedy the situation, the 
error ellipses should be scaled by the a posteriori variance factor. 

B-50. To confirm the quality of the observations, the standardized residuals 
should be checked for outliers. The checking of the statistics often involves 
critical evaluation of the a priori standard deviations of the observations. If 
the baseline variance/covariance matrix is routinely modified by a multiplier, 
documentation of a measurement over a test network may be required as 
confirmation of the multiplier used. 

B-51. To conform to the internal consistency requirements for a particular 
geometric accuracy, the error ellipses should confirm the capability of the 
network design to meet the specifications. The standardized residuals and the 
estimate of variance should confirm that the observations have actually met 
the required standard. 

B-52. All points in a survey should conform to the specifications belonging to 
the relevant classification. This applies whether the points are connected by 
baseline observations or not. This is also valid when relative accuracy values 
are calculated to points with previously established coordinate values. Geoid- 
separation values are applied to orthometric heights of points that will be 
constrained in the transformation and adjustment. 

DERIVATION OF GEOI D-SEPARATION VALUES 

B-53. The foil owing four methods are used for determining geoid heights: 

• Geodetic-leveling-geoid method. The use of a geodetic-leveling 
geoid. 

• Global-geopotential-model method. The use of different types of 
global-geopotential models derived from gravity and active or passive 
satellite information. 



B-16 Control-Survey Standards 



FM 3-34.331 



• Gravimetric method. The use of an intensive grid of local gravity, 
together with a high-degree global-geopotential model. 

• Geometrically modeled geoid method. The use of a geometrically 
modeled geoid by contouring geoid-height values derived from 
orthometricand ellipsoidal heights. 

B-54. The relative accuracy of height values resulting from the global- 
geopotential-model method are dependent on the grid spacing of the 
geopotential model used. The spacing of points with observed local gravity in 
the gravimetric method and the spacing of leveled points in the geometrically 
modeled geoid method determine the relative accuracy. 

B-55. Thegeodetic-leveling-geoid method is generally not accurate enough to 
convert G PS-ellipsoidal heights intoorthometric heights but works well with 
height differences. Theglobal-geopotential-model method is useful in the case 
of long baselines in an area with a smooth geoid and scarce orthometric-height 
points. The gravimetric method is the most accurate when a sufficient dense 
grid of gravity information is available. The geometrically modeled geoid 
method is the most accurate when sufficient orthometric information is 
available. When orthometric information is scarce and the geoid is not 
smooth, surface fitting and contouring are not recommended for short 
distances (10 kilometers or less). 

TRANSFORMATION AND CONSTRAINED ADJ USTMENTS 

B-56. The next step is the derivation of transformation parameters between 
the minimally constrained adjusted vectors and the selected constrained 
points in the local geodetic system. This is usually carried out together with a 
constrained least-squares adjustment. This adjustment is subjected to the 
same analysis as the minimally constrained adjustment. Error ellipses are 
calculated again and the network is allocated an accuracy order that enables 
its orderly integration with the database that contains the existing data set of 
established coordinates. 

NOTE: Refer to E M 1110-1-1003 for a complete sample of an 
adjustment statistics summary. 



Control-Survey Standards B-17 



Appendix C 

Basic Survey Computations 

This appendix contains recommended procedures for performing basic 
survey computations. Until recently, three different forms were used to 
compute a two-point intersection. Army units have developed a one-sheet 
format (FigureC-1, pageC-2) to use when computing a two-point 
intersection. This one-sheet format is broken down into three parts and 
combines portions of DA Forms 1920, 1938, and 1947. Part I is from 
DA Form 1920, Part II is from DA Form 1938, and Part III is from 
DA Form 1947. 

COMPUTATION OF ATWO-POINT INTERSECTION 

C-l. Tabulate data (known and field) for a two-point intersection on 
DA Form 1962 (FigureC-2, pageC-3) or on a blank piece of paper with an 
identifying heading. Includethefollowing information: 

• A properly oriented sketch of the triangle with the known baseline 
stations, an unknown station, and any other information that may be 
needed to organize computations. Label the unknown point as 
number 1 and the known points (clockwise from the unknown point) 
as number 2 and number 3. 

• The position and elevation of known stations. 

• The grid azimuth and grid distance of the known baseline. 

• The observed horizontal angles, ZDs, and H I s. 

NOTE : The grid azimuth (denoted by t) and the grid distance may be computed on 
DA Form 1934 by using UTM coordinates. If needed, conversions can be computed on 
DA Forms 1932 and 1933. 

COMPLETE PART I OF THE ONE-SHEET FORMAT 

C-2. Perform thefollowing steps tocomplete Part I (FigureC-1): 

Step 1. Abstract all pertinent information from DA Form 1962 onto Part I. 
Includethefollowing information: 

• Record the— 

Project name. 

Project location. 

Organization performing the survey. 

Date of computation. 

• Record the station names (under the station column) opposite 
their respective numbers. Station 1 (unknown station) and 
Stations 2 and 3 (known stations). 



Basic Survey Computations C-1 



FM 3-34.331 











24 PROJECT 

Example 


TWO-POINT INTERSECTION 
(OBSTRUCTION COMPUTATION) 




LOCATION 

Fort Wainwright, Alaska 


ORGANIZATION 

DMS7BGS 


DATE 

Today's date 


STATION 


OBSERVED 
ANGLE 


SINE 


DISTANCE 




SIDE 


1ANT1 


37°17'26.6" 


+0.605859583 


2934.878 


2-3 


BHTW-CTWR 


2BHTW 


82°07'00.9" 


+0.990550001 


4798.378 


1-3 


ANT 1-CTWR 


3CTWR 


60°35'32.5" 


+0.871148354 


4219.978 


1-2 


ANT 1-BHTW 


I D=Hatio, side/sine 4844.155448 


Part I ? DA Form 1920 






a*a 


156°34'32.0" fl 




t3B2 


336°34'32.0" 




*a 


82°07'00.9" 1 


-Z3 


60°35'32.5" 




shicbi) 1 -0.854390566 


I2tol 


238°41'32.9" 


htptol) 


-0.994552512 


Otil 


275°58'59.5" 


cwau) | -0.519631370 


A 




astcstoi) 


+0.104236753 






N 2 


7193431.450 


2 


BHTW 


1^2 


469533.340 


Nj 


7190738.450 


3 


CTWR 


E 3 


470700.070 


A 

N 


-2192.833 


S 


4219978 


AE 


-3605.509 


A 

N 


+500.167 


S 


4798378 


AE 


-4772.239 


N, 


7191238.617 


1 


ANT1 


Ei 


465927.831 


N, 


7191238.617 


1 


ANT1 


E, 


465927.831 


Part II, DA Form 1938 


Station 1, occ 


BHTW 




CTWR 


t2tol=(t2to3+^2) 
t3tol=(t3to2-Z3) 










TJi 


Station 2, obs 


ANT1 




V 








Object sighted 


Top of Ant 


Top of Ant 










c, 


92°06'00.5" 




89°35'16.2" 










a and mean tj> 


238°42764°51' 




275°59764°51' 










(0.5 -m) 


0.4290 




0.4290 


s 


4219.978 




4798.378 


psinl 


30.997 




31.007 


K in sees 


58.4" 




66.4" 


(90°-C,+K> 


-02°05'.02.1" 




+00°25'50.2" 


tan(90 o -d+K) 


-0.036387254 




+0.007515723 


























h 2 -h, 


-153.553 




+36.063 


h, 


345.786 




156.208 


HI 


1.699 




1.421 


Corrected elevation 


193.932 




193.692 


h 2 -h, = s • tan(90°-?i+K) K in sees = IM^s 

p sin 1 

Part III, DA Form 1947 


COMPUTED BY 

SSG BAKER 


DATE 

01 SEP 98 


CHECKED BY 


DATE 









Figure C-1. Sample One-Sheet Format for Basic Survey Computations 



C-2 Basic Survey Computations 



FM 3-34.331 





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4W.53J.340 




E 


47O r 700.O™ 


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uss'm^s.o - 




















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fHttttJBV 

MH: WMivwinh 


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Figure C-2. Sample DA Form 1962 



Basic Survey Computations C-3 



FM 3-34.331 



Step 2. 



Record the observed horizontal angles opposite their respective 
numbers under the observed-angle column. 

Record the distance of the given side (side 2-3) that serves as the 
baseline under the distance column. 

Record the station names that correspond to each side under the 
side column. 
Complete the following items in Part I: 

Compute the unknown angle (number 1) by subtracting the two 
observed angles from 180°. 

Compute the sine of angle number 1 and record to nine decimal 
places with the sign (round the answer). 

Compute the side/sine ratio (denoted by D) by dividing the 

distance of the given side (side 2-3) by the sine of angle number 1 

and record to six decimal places (round the answer). 

Compute the sine of angle number 2 and record to nine decimal 

places with the sign (round the answer). 

Compute side 1-3 by multiplying the sine of angle number 2 by D 

and record to three decimal places (round the answer). 

Compute the sine of angle number 3 and record to nine decimal 

places with the sign (round the answer). 

Compute side 1-2 by multiplying the sine of angle number 3 by D 

and record to three decimal places (round the answer). 



COMPLETE PART II OF THE ONE-SHEET FORMAT 

C-3. Perform the following steps to complete Part 1 1 (FigureC-1, pageC-2): 

Step 1. Abstract all necessary information from DA Forms 1962 and Part I 
onto Part 1 1 . Record t he- 
Project name. 

Project location. 

Organization performing the survey. 

Ellipsoid name. 

Zone number. 

Meridian designation. 

t(2to3). 

t(3to2). 

Angle at Station 2 (Z 2). 

Angle at Station 3 (Z 3). 

Northing and easting of Station 2 (N 2 and E 2 ). 

Northing and easting of Station 3 (N 3 and E 3 ). 

Station names opposite their appropriate numbers (for example, 

2 ABE, 1 Pole, or 3 CAT). 

Grid distance of side 1-2 (from Part I). 

Grid distance of side 1-3 (from Part I). 



C-4 Basic Survey Computations 



FM 3-34.331 



Step 2. Complete the following items: 

Computet (2 to 1) by adding Z 2 tot (2 to 3). If the sum exceeds 

360°, subtract 360°. 

Compute the sine of t (2 to 1). Record to nine decimal places with 

the sign (round the answer). 

Compute the dE by multiplying the sine of t (2 to 1) by the grid 

distance of side 2-1. Record to three decimal places with the sign 

(round the answer). 

Compute Ei by algebraically adding dE and E 2 . Record to three 

decimal places. 

Compute the cosine of t (2 to 1). Record to nine decimal places 

with the sign (round the answer). 

Compute the dN by multiplying the cosine of t (2 tol) by the grid 

distance of side 2-1. Record to three decimal places with the sign 

(round the answer). 

Compute Ni by algebraically adding dN and N 2 . Record to three 

decimal places. 

Compute t (3 to 1) by subtracti ng the Z 3 from t (3 to 2). I f Z 3 is 

larger than t (3 to 2), add 360° before subtracting. 

Compute the sine of t (3 to 1). Record to nine decimal places with 

the sign (round the answer). 

Compute dE by multiplying the sine of t (3 to 1) by the grid 

distance of side 3-1. Record to three decimal places with the sign 

(round the answer). 

Compute Ei by algebraically adding dE and E 3 . Record to three 

decimal places. 

Compute the cosine of t (3 to 1). Record to nine decimal places 

with the sign (round the answer). 

Compute dN by multiplying the cosine of t (3 to 1) by the grid 

distance of side 3-1. Record to three decimal places with the sign 

(round the answer). 

Compute N ± by algebraically adding dN and N 3 . Record to three 

decimal places. 

NOTE: Compare the two sets of N 1 and E^ They must agree to within O.OOl. If they do 
not, then a math or abstraction error was made, and Part 1 1 must be recomputed. 



COMPLETE PART III OF THE ONE-SHEET FORMAT 

C-4. Perform thefollowing steps to complete Part 1 1 1 (FigureC-1, pageC-2): 

Step 1. Abstract all information from DA Forms 1962 and Part 1 1 onto 
Part III. Record the- 

Prqject name. 

Project location. 

Organization performing the survey. 

Date of computation. 

Name of the station whose elevation is known (Station 1, 

occupied). 



Basic Survey Computations C-5 



FM 3-34.331 



• Name of the station whose elevation is unknown (Station 2, 
observed). 

• Object sighted (for example, target or obstruction light). 

• Mean observed ZD (denoted by ^). 

• Mean latitude (denoted by §) and the azimuth of a line (denoted 
by a). 

NOTE : The azimuth of a line is recorded to the nearest minute and is obtained from 
Part II. The mean latitude is obtained by converting the northings and eastings 
computed on Part 1 1 to geographic positions and then taking the mean of the latitudes. 

• Weighted mean coefficient of refraction (0.5 - m). When this is 
not observed, use 0.4290. 

• Grid distance (denoted by s) (from Part 1 1 ). 

• Elevation of the occupied station (denoted by h{) (from 
DA Form 1962). 

• H I of the station occupied (from DA Form 1962). 
Step 2. Compute the elevation by using the following formulas: 

• Compute rho (denoted by p) sine 1". Record to three decimal 
places (round the answer), p is the mean radius of curvature in 
the plane of the distance and will be given (it can be found on 
DA Form 1962). 

RN 
P = 



2 2 

Rsin a + Ncos a 



where- 

R = radius of curvature in the plane of the meridian (obtained 

from NIMA 's table generating software) 
N = radius of curvature in the plane of the prime vertical 

(obtained from NIMA 's table generating software) 

Compute the correction for the earth's curvature (denoted by k) 
in seconds (denoted by sees). Record to one decimal place (round 
the answer). 

,. , (0.5 -m)s 

K(msecs) = - — , ,,; 

psinl 

where— 

m = mean coefficient of refraction 

Compute (90° -i^+K). Record to one decimal place (00.1") with 

the sign (k must be converted to minutes and seconds if it is over 

60"). 

Compute the tangent of (90° - Ci+ K )- Record to nine decimal 

places with the sign (round the answer). 

Compute h 2 - h^ Record to three decimal places with the sign 

(round the answer). 

h 2 -h ± =s • tan(90°- Ci + k) 



C-6 Basic Survey Computations 



FM 3-34.331 



• Compute the corrected elevation by algebraically adding (h 2 - 
h]), h 1( and HI. 

• Repeat Part III, steps 1 and 2, for observations taken from the 
other end of the baseline. 

• Sign and date the form. 

NOTE: Compute the DE between the two computed elevations. Use the following 
formula to determine the AE: 



AE - 0.5 in • J distance to point in km 

Use the shortest of the two distances to the unknown point. If theDE is larger than the 
AE, check for math and abstraction errors. If none are found, the intersection does not 
meet specifications and needs to be reobserved. 

COMPUTATION OF A GRID TRAVERSE AND SIDE SHOTS 

C-5. DA Form 1940 is used to compute a grid traverse. Tabulate known and 
field data for the traverse on a DA Form 1962 (FigureC-3, pageC-8) or on a 
blank piece of notepaper with an identifying heading. I ncludethe following: 

• A sketch of the traverse. I ncludethe starting and ending stations, the 
intermediate stations, and any other information that may be needed 
to organize the computations. 

• The position, the elevation, and the azimuth (if known) for the 
starting and ending stations. 

• The observed angles and distances. 

C-6. FigureC-4, pageC-9, shows a completed DA Form 1940. This figure is 
further broken down into separate figures to demonstrate the computation 
process. Refer to FiguresC-5 and C-6, pageC-10, when working step 1 and 
FigureC-7, pageC-11, when working steps 2 through 7. 

Step 1. Transfer the information from DA Form 1962 to DA Form 1940. 
Record the following information: 

Project name. 

Project location. 

Organization performing the survey. 

From station (starting station). 

To station (ending station). 

Number of angle stations (number of observed field angles). 

Grid zone. 

Traverse station names (the first and last columns of 

DA Form 1940). 

Observed angles (corrected mean station angles). 

Corrected field distances. 

Starting and ending projected geodetic azimuths (denoted byT). 

Mean elevation. 

Starting and ending UTM grid coordinates. 



Basic Survey Computations C-7 



FM 3-34.331 





For use of this form, see FM 3-34.331 the proponent agency is TRADOC. 






PROJECT 

Example 1 


TABULATION OF GEODETIC DATA 




LOCATION 

Fort Belvoir, Virginia 


ORGANIZATION 

DMS 


STATION 


Third-Order, Class I Traverse 


TILDON to ABBOT 


Grid Zone: 
18S 










ABBOT A 




























MARINE 


ff to ABBOT 


AZMARK 


A 












N 
















ARMY r{ 


























^ 










^ 


9 










^. 






Mean elevation of 


traverse = 73 m 














**""-Q AIR FORCE 














TILDON N 


4,283,839.177 






to JOBIE 

M 


E 


314,225.155 






/ 








TILDON £\^ 




JOBIE N 


4,284,279.027 








E 


315,123.186 




ABBOT N 


4,287,595.893 








E 


310,461.502 


az (T) TILDON to 


JOBIE 








63°54'20.3" 






ABBOT AZ N 


4,286,241.633 








E 


311,106.466 












Field 


Angles 




az (T) ABBOT to 


ABBOT AZ MARK 


TILDON 


263°24'13.6" 




154°32'02.9" 




AIR FORCE 


149°47'12.2' 








ARMY 


281°21'15.3" 




Geodetic 


Distance (m) 


MARINE 


152°22'39.3" 




TILDON-AIR FORCE 


1,613.478 


ABBOT 


323°42'12.5" 




AIR FORCE-ARMY 


3,777.908 








ARMY-MARINE 


724.196 






(horizontal tape) 


MARINE-ABBOT 


112.372 


TABULATED BY 

GySgtCook 


DATE 

14 August 80 


CHECKED BY 

SFC Edwards 


DATE 

14 August 80 




DA FORM 1962, FEB 57 usappcvi.oo 





Figure C-3. Observed Angles and Distances on DA Form 1962 



C-8 Basic Survey Computations 



FM 3-34.331 




o 

O) 

1— 

E 
o 

LL 
< 

a 


Q. 

E 
o 
O 

Q. 

E 

TO 

en 

6 



&_ 

3 



Basic Survey Computations C-9 



FM 3-34.331 



jt?a.£ 



srtmpifi 






ftt.FWee 






***** 



AflfluT 



Afticr.^ 



■i ^ 



a''j | - , '?i" 



jjtjr^'tf.j- 1 



- "i i 



mm 
t-j l. j>e 



ȣ_LL3!_Jf?LtL^ 



''J.^n-i" 



"iTAMl 



j>j: i 




±*n 



JY 

J-« H 



1MJI ELEI/. 






I fcri ■ ■ i I 



>-/ist. All. A 



*_a!waaM 






Figure C-5. Example 1 (Portion of DA Form 1940) 



AT ION CH THE UNIVERSAL TRANSVERSE MEHCATOR GRID 



lalMiim 



■ s&mmhv 



t rf iJJliH, 



ttl BECffiOJ 






15 * ■ ' ■ 



nrgJ 






t^15ki?ll- 



+ *m.-Hb 



- tTul. jJ-T 



- jTtv^a 




Figure C-6. Example 2 (Portion of DA Form 1940) 



C-10 Basic Survey Computations 



FM 3-34.331 



SAaaP^-E 



4mm in h e is 



**>*-!/£•' 




'T.VI.H.,: Q .-.ill. 



H** 







HI ■ ■■ ! i 



~-?-i 



itt_ 



*.■: - _z 



an 



-nVT 



iiiaiJL 



*,'&--: *Bi 



=*L 



^ 



TJ- 




. M^Jri.oJ 













j-U 






'■"■-I 



DA-VtlfeCQ 



Figure C-7. Example 3 (Portion of DA Form 1940) 

NOTE: The starting and ending T may be obtained from UTM coordinates by 
computing t and (t -T) on DA Form 1934. 

Step 2. Compute the summation of angles (L ^s) by adding all of the 
observed angles to the starting back azimuth. Leave the sum in decimal 
degrees. Record on DA Form 1940 to six decimal places (round the answer). 
Step 3. Compute the ending azimuth by subtracting 180 s from theL ^s until 
it is as close as possible to the known ending azimuth. Record on 
DA Form 1940 in degrees, minutes, and seconds. Record seconds to one 
decimal place (round the answers). 

Step4. Compute the AEC by subtracting the fixed (known) ending azimuth 
from the computed ending azimuth. Compute to one decimal place with the 
sign. Record in the 'Total Angular Closure" block on DA Form 1940. 



Basic Survey Computations C-11 



FM 3-34.331 



NOTE: The AEC is always equal to the computed values minus the fixed values as 
shown in the following formula: 

Computed ending azimuth = 154231'53.2" 

Fixed ending azimuth = - 154232X)2.9 " 

AEC = -9.7 

Step 5. Computethe allowable AEC by using theformula from DMS Special 
Text (ST) 031. Since this is a third-order, Class I traverse, theformula used 
for computing the AE is ±10"Jn, where N is the number of segments or 
distances. This traverse has four distances; therefore/\E =±10"j4 =±20.0". 

NOTE : The AE is always truncated. Do not round up the AE, because rounding will 
allow more error. Record to one decimal place. 

Step 6. Compute the correction per station by dividing the AEC by the 
number of observed angles, then change the sign of the answer. Record to two 
decimal places with the sign, and truncate the answer. 

-AEC -09.7" 

Correction per station = ; — ; ; ; — = '■ — =-(-1.94") =+1.94" 

number of observed angles 5 

NOTE : No one angle contains more of the error than another since the angular error is 
accidental. The error must be distributed evenly among the station angles. 

Step 7. Compute the correction per observed angle and properly assign 
corrections to be applied to the observed angles. Record to one decimal place 
with the sign. After computing the correction per station, if the division does 
not result evenly to 0.1", produce a group of corrections that are within 0.1" of 
each other as in the following example. 

+1.94" +2.0" 

2 @ +2.0" = +4.0" 

or 

3@ +1.9" = +5.7 " 
+9.7" +9.7" 9.7" total correction 

C-7. After computing the correction per angle, assign the proper correction to 
each angle. For uniformity, apply the larger corrections to the larger angles. 
Record the correction per station in the "Angular Closure Per Station" block 
on DA Form 1940 (for example, 2 @+2.0" and 3 @+1.9"). Sum the corrections. 
Record in the appropriate block on DA Form 1940. 

NOTE: The sum of the corrections must equal the AEC, with the opposite sign. For 
example, if the AEC is negative, the corrections will be positive. If the AEC is positive, 
the corrections will be negative. 



+1.94" 




+2.0' 


+1.94" 


or 


+1.9' 


+1.94" 




+1.9' 


+1.94" 




+1.9' 



C-12 Basic Survey Computations 



C-8. Refer to FigureC-8 for working steps 1 through 4. 



FM 3-34.331 



SftjjlfrLG 



'- *■■>« 



iin-i w ty ,? as 



IT* no** 

5 






tl Ljo* 



i£*i£ - 



AJJJ.V 



y* *-»* 



AflAOT 



r A61i 



kt'ii'pi 



i£X<L''t.. 



Ww-'jftg.". 



ltfl'47'M.l' 



.-HTTjijEjeJ* 



^ftiiQUV 



isrji'.uf" 



nijeiiia!! 



M'jli'fll.i' l 



■ ■f *» 



IJflflMf 



n,«mn 



Figure C-8. Example 4 (Portion of DA Form 1940) 

Step 2. Compute the adjusted angles by algebraically adding the correction 

per angle to the observed angle. Record to one decimal place. 

Step 2. Compute the azimuth of each traverse section by adding the first 

adjusted angle to the starting back azimuth. If the azimuth is over 360 s , 

subtract 360 s . This is the azimuth to the forward station. The azimuth of all 

lines must always be stated in the direction that the traverse is being 

computed. 

Starting back azimuth = 63 9 54'20.3" 

Adjusted angle at TILDON = 263224'15.5" 

Forward azimuth: TILDON to AIR FORCE = 32721835.8" 



Step 3. Convert the forward azimuth of the line to a back azimuth by either 
adding or subtracting 180 s from the forward azimuth. The forward azimuth to 
the next station is then computed by adding the back azimuth from the 
previous line to the adjusted angle of the next station. If the new forward 
azimuth to the station is greater than 360 s , subtract 360 s . 



Forward azimuth: TILDON to AIR FORCE 

Back azimuth: TILDON to AIR FORCE 
Adjusted angle at Al R FORCE 
Forward azimuth: AIR FORCE to ARMY 



32731835.8" 
- 180 W00. (T 

14731835.8" 
+ 149847141 " 

297S05'49.9" 



Basic Survey Computations C-13 



FM 3-34.331 



Step 4. Repeat this procedure until the final station obtains a perfect check. 
The computed closing azimuth must agree exactly with the known closing 
azimuth. If not, a math error has been made and must be corrected. 

NOTE: It is very important that particular attention be given to the direction of the 
azimuth. An error of 180- may go undetected, and two errors of 180 s will cancel out 
(providing a final azimuth check). This will result in some sections being reversed in 
direction. Always refer to the sketch provided with the surveyor's field notes. 

C-9. Refer to FigureC-9 when working steps 1 through 10. 




Figure C-9. Example 5 (Portion of DA Form 1940) 



C-14 Basic Survey Computations 



FM 3-34.331 



Step 2. Compute the SLC. Record to six decimal places. 

SLC '° 7 -! = i " 6^000 = - 99 " 89 

where- 
in = the mean elevation 
R = the mean radius of the earth (Ifh is in feet, use R = 20,906,000 feet. I f h 

is in meters, useR =6,372,000 meters.) 
Step 2. Compute the middle northing (denoted by MID N) and the middle 
easting (denoted by MID E). To compute the MID N, add the northing of the 
begi nni ng traverse station to the northi ng of the endi ng traverse station. Then 
divide by two. Record to the nearest 1,000 meters. To compute the M I D E , add 
the easting of the beginning traverse station to the easting of the ending 
traverse station. Then divide by two. Record to the nearest 1,000 meters. 

Northing for Tl LDON = 4,283,839.177 m Easting for Tl LDON = 314,225.115 m 
Northing for ABBOT = +4.287.595.893 m Easting for ABBOT = +310.461.502 m 

8,571,435.070 624,686.617 
- — -z rn — '—- m 

2 2 

= 4,285,717.535 m = 312,343.3085 m 

MID N = 4,286,000 m MID E = 312,000 m 



NOTE : A scale factor (denoted by K) is required to convert a measured distance to a 
grid distance. A mean K may be computed for the entire traverse or for each section in 
the traverse. For this example, a single K will be used since the traverse's total length 
is 8,000 meters or less. Traverses over 8,000 meters require a K to be computed for each 
section. Compute the northing and easting of the midpoint for the desired traverse or 
section to the nearest 1,000 meters. Record the formula in the appropriate block on 
DA Form 1940. 

Step 3.ComputeK. Record to six decimal places (round the answer). 

K =KJ1 +(XVIII)q 2 +0.00003q 4 ] 

where— 

K = the scale factor at the CM (0. 9996) 

XVIII = theT able 18 value 

q = a factor used to convert E 'to mi months 



Basic Survey Computations C-15 



FM 3-34.331 



Step 4. Obtain the Table 18 (denoted by XVIII) value. The XVIII value is 
extracted from the tables in DMS ST 045, using the MID N as the argument. 
I nterpolate to compute the XVI 1 1 value to six decimal places (round the 
answer). An example follows: 

MIDN XVIII Value 

1) 4,200,000 1) 0.012321 

2) 4,286,000 2) Unknown 

3) 4,300,000 3) 0.012318 

MIDN(2)-MIDN(1) _ XVIII (2) -XVIII (1) 
MIDN (3) -MIDN (I) ~ XVIII (3) -XVIII (I) 

4,286,000 - 4,200,000 _ XVIII (2) - 0.01232 1 
4,300,000-4,200,000 ~ 0.012318-0.012321 

86,000 = XVIII (2) - 0.012321 
100,000 ~ -0.000003 

„ „ , XVIII (2) -0.012321 
°- 86 = -0.000003 

XVIII (2) -0.012321 = 0.86(-0.000003) 
XVIII (2) -0.012321 = -0.00000258 

XVIII (2) = 0.012321-0.00000258 

XVIII (2) = 0.01231842 
» 0.012318 



Step5. Compute E' by subtracting 500,000 from the MID E. Record to 
1,000 meters as an absolute value. 

E'=MID E - 500,000 =312,000 - 500,000 =-188,000 m 

where— 

E' = absolute value of MID E 



C-16 Basic Survey Computations 



FM 3-34.331 



Step 6. Compute q by multiplying E' by 0.000001. Record to six decimal 
places (round the answer). 

q =E'« 0.000001 =188,000 • 0.000001 =0.188000 

where— 

q=a factor used to convert E 'mi Months 

Step 7. Compute q 2 and q 4 . Record to six decimal places (round the answers). 

q 2 = 0. 188000 2 = 0. 035344 
cf=0. 188000 4 = 0. 001249 

Step 8. ComputeK. Record tosixdecimal places (round the answer). 

K =KJ1 + (XVII I) 0^ + 0.00003 q 4 ] 

= 0.999611 +0.012318 • 0.035344 +0.00003 • 0.001249] 
= 1.000035 

where— 

K = the scale factor at the CM (0.9996) 

q=a factor used to convert E 'mi Months 

Step 9. Compute a scale factor used to reduce the grid distance (denoted by 
K*) by multiplying K by the SLC. Record to six decimal places (round the 
answer). 

K*=K • SLC =1.000035 • 0.999989 =1.000024 

NOTE: After computing K and K>, record the values in the "Scale Factor x SLC" blocks 
on DA Form 1940 beside the appropriate corrected field distance. 

Step 10. Compute grid distances as follows. 

• Taped distances (corrected horizontal field distances) are 
reduced to grid distances by multiplying the taped distance by 
K*. 

G =H • K* 

where— 

G = grid distance 

H = taped distance 



Basic Survey Computations C-17 



FM 3-34.331 



• EDME distances (reduced geodetic distances) are corrected by 
multiplying the geodetic distance by K. 

G=S ' K 

where— 

G = grid distance 

S = geodetic distance 

NOTE : Compute the total length of the traverse. Record to three decimal places in the 
"Length of Traverse" block on DA Form 1940 (FigureC-10). 



TRAVERSE lyQMPUTATIQN OPT TKE UNIVERSAL TflAPC 



■'-11 *noN 




( ixEi. 



ttict 



g"»P.3JT 



ZOM 



t^Mfi *XT5^a*tr -tlba-«i 



-aTJ^uii- 



I'.ur 



-to .JUL. 



Figure C-10. Example 6 (Portion of DA Form 1940) 

C-10. Refer to FigureC-11 when working steps 1 through 3: 

Step 2. Compute the cosines and sines of the azimuths. Record to seven 
decimal places with the sign (round the answer). 

Step 2. Compute the dN sand thedEs. 

• The dN is computed by multiplying the grid distance by the 
cosine of the azimuth. Record to three decimal places with the 
sign (round the answer). 

dN =grid distance • cos (t) 

• ThedE is computed by multiplying the grid distance by the sine 
of the azimuth. Record to three decimal places with the sign 
(round the answer). 

dE =grid distance • sin (t) 



C-18 Basic Survey Computations 



FM 3-34.331 



IMPUTATION on the: UNIVERSAL TRANSVERSE h 







&at £— iJEZIkill 




.HJ4..TII 



=**L'JL 



ITfcAiJZT 



jytijajdj 






j^-S-C » fi-Si-i*' £j¥|-: 



Figure C-11. Example 7 (Portion of DA Form 1940) 

Step 3. Compute errors i n the dN and the dE (denoted by E n and E e). 

• Compute the En by using the following formula. Record to three 
decimal places with the sign. 

En = computed dN - fixed dN 

Algebraically add the column of dNs to get the computed dN. 
Record to three decimal places with the sign. 

+1,357.957 
+1,720.902 

+567.159 

+110.373 



Computed dN = +3,756.391 

Subtract the fixed starting northing from the fixed ending 
northing to get the fixed dN. Record to three decimal places with 
the sign. 

Fixed ending northing = +4,287,595.893 
Fixed starting northing = +4,283,839.177 
Fixed dN = +3,756.716 

En =computed dN - fixed dN =+3,756.391 - (+3,756.716) =-0.325 



Basic Survey Computations C-19 



FM 3-34.331 



Compute the Ee by using the following formula. Record to three 
decimal places with the sign. 

Ee = computed dE - fixed dE 

Algebraically add the column of dEs to get the computed dE . 
Record to three decimal places with the sign. 

-871.461 

-3,363.344 

+450.363 

+21.115 



Computed dE = -3763.327 

Subtract the fixed starting easting from the fixed ending easting 
to get the fixed dE. Record to three decimal places with the sign. 

Fixed ending easting = +310,461.502 
Fixed starting easting = +314,225.115 
Fixed dE ' = -3,763.613 

Ee = computed dE - fixed dE =-3,763.327 - (-3,763.613) = +0.286 

C-ll. Refer to FigureC-12 when working steps 1 through 5. 

Step 2. Compute the LEC. Record to four decimal places in the "Linear 
Closure Ratio" block on DA Form 1940. Compute the LEC by using the 
following formula: 

LEC = J En 2 + Ee 2 = <J(-0.325) 2 + 0.286 2 

= J0.105625 + 0.081796 = 0.4329 

Step 2. Compute the RC. Round down to the nearest 100. Record in the 
"Linear Closure Ratio" block on DA Form 1940. Compute the RC by dividing 
the length of traverse (in meters) bytheLEC. Use the following formula: 

RC = ^ length of traverse (m) = j. 6,228-170 = 1:U>mo87 = hu>200 

Step3. Compute the AE for position closure. Since this is a third-order, 
Class I traverse, the AE for position closure is equal to 0.4 times the square 
root of the distance of the traverse in kilometers. Compute the AE for position 
closure by using the following formula (found in DMS ST 031) (truncate and 
record the answer to four decimal places): 

AE = (0.4) Jk = {0.4)46.22817 = 0.9982 

where— 

k = the distance of the traverse in kilometers 



C-20 Basic Survey Computations 



FM 3-34.331 



»MSE CUMIIf rATI<>»* ON THE UHIVWWI. 



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Figure C-12. Example 8 (Portion of DA Form 1940) 



NOTE : The L E C must be compared to the AE . I f the L E C is equal to or less than the AE , 
the traverse has met specifications. If the LEC is greater than the AE, no further 
computations are necessary. 

Step 4. Compute the correction factors (correction to northing [denoted by 
KN] and correction to easting [denoted by KE]) to be used in adjusting the 
traverse. 

• KN is computed by dividing the En by the length of traverse in 
meters then changing the sign of the answer. Record to seven 
decimal places with the sign (round the answer). 



KN 



En 



length of traverse 



-0.325 
6,228.170 



+0.0000522 



KE is computed by dividing the Ee by the length of traverse in 
meters then changing the sign of the answer. Record to seven 
decimal places with the sign (round the answer). 



KE = 



Ee 



length of traverse 



+0.286 
6,228.170 



= -0.0000459 



Basic Survey Computations C-21 



FM 3-34.331 



NOTE: A correction factor will always have the opposite sign of the En and the Ee. 

Step 5. Compute corrections to dN sand dEs. 

• Corrections to dNs are computed by multiplying KN by the grid 
distance. This is done for each section of the traverse. Record to 
three decimal places with the sign (round the answer). 

Correction todN =KN • grid distance 

= 10.0000522 • 1,613.534 (first distance) 
= 10.084 

• Corrections to dEs are computed by multiplying KE by the grid 
distance. This is done for each section of the traverse. Record to 
three decimal places with the sign (round the answer). 

Correction todE =KE • grid distance 

= -0.0000459 • 1,613.534 (first distance) 
= -0.074 

• After all the corrections are recorded, sum the columns. The sum 
of the corrections must equal the errors of dN and dE with the 
opposite sign. If, because of rounding errors, the sum does not 
exactly equal the error of dN or dE, this difference must be 
distributed. For uniformity, the largest corrections are changed 
by one unit (third decimal place) until the correct sum is 
obtained. 







Correction 




dN_ 


dE_ 


todE 


New dE 


10.084 


-0.074 




-0.074 


10.197 


-0.173 


-0.001 


-0.174 


10.038 


-0.033 




-0.033 


10.006 


-0.005 




-0.005 



10.325 -0.285 -0.286 



The sum of the dN corrections is exactly equal to the error 
(-0.325) with the opposite sign. 

The sum of the dE corrections is different by 0.001 from the error 
(40.286). Therefore, an additional 0.001 is applied to the largest 
correction (0.173). 



C-22 Basic Survey Computations 



C-12. Refer to FigureC-13 when working steps 1 and 2. 



FM 3-34.331 



TRANSVERSE MERCATOR GRIQ 




fefetsE^y^*: 






kt<>**- 



Figure C-13. Example 9 (Portion of DA Form 1940) 

Step 2. Compute the adjusted grid coordinates (northings and eastings). 

• Tocomputethe adjusted northing, algebraically add thedN and 
the correction of dN to the northing of the preceding station. 
Record to three decimal places. 



dN 

Correction to dN = 

N orthing for TILDON 
Northing for AIR FORCE = 



+1,357.957 

+0.084 

+4.283.839.177 

+4,285,197.218 



• To compute the adjusted easting, algebraically add the dE and 
the correction of dE to the easting of the preceding station. 
Record to three decimal places. 



dE 

Correction to dE = 

Easting for TILDON 
Easting for AIR FORCE 



-871.461 

-0.074 

+314.225.115 

+313,353.580 



NOTE: Continue in a like manner for each station. As a math check, apply the last dN 
and the last correction of dN to the northing of the preceding station. The answer must 
equal the fixed northing of the closing station. The same is true for the easting. 

Step 2. Sign and date the form. 



Basic Survey Computations C-23 



FM 3-34.331 



COMPUTATION OF A C-F ACTOR 



C-13. Compute the C-factor. Record on DM S Form 5820-R. Refer to 
FigureC-14 and FigureC-15, pageC-26, when working steps 1 through 15. 
The step numbers correspond to the numbered blocks on FigureC-14. 
FigureC-15 shows a completed DMS Form 5820-R. 

Step 2. Complete the heading information (1). 

Step 2. Record the stadia constant for the instrument (2). 

Step 3. Record the backsight-rod (near-rod) readings (in millimeters) (3a). 

• Compute and record stadia intervals (in millimeters) (3b). If the 
difference is greater than 3, reobserve. 
Compute and record the sum of the intervals (3c). 
Compute and record the mean middle-wire reading (in 
millimeters) toonedecimal place (3d). 

Compute and record the sum of the three-wire readings (in 
millimeters) (3e). 
Step 4. Record the foresight-rod (far-rod) readings (in millimeters) (4a). 

Compute and record the stadia intervals (in millimeters) (4b). If 
the difference is greater than 3, reobserve. 

Compute and record the sum of the intervals (4c). 
Compute and record the mean middle-wire reading (in 
millimeters) toonedecimal place (4d). 

Compute and record the sum of the three-wire readings (in 
millimeters) (4e). 
Step5. Record the backsight-rod (near-rod) readings (in millimeters) (5a). 

Compute and record the stadia intervals (in millimeters) (5b). If 
the difference is greater than 3, reobserve. 

Compute and record the sum of the intervals (5c). 
Compute and record the mean middle-wire reading (in 
millimeters) toonedecimal place (5d). 
Step 6. Record the foresight-rod (far-rod) readings (in millimeters) (6a). 

Compute and record the stadia intervals (in millimeters) (6b). If 
the difference is greater than 3, reobserve. 
Compute and record the sum of the intervals (6c). 
Compute and record the mean middle-wire reading (in 
millimeters) toonedecimal place (6d). 
Step 7. Compute and record the cumulative totals as follows: 



3e + the sum of the second set of near-rod readings from 5a (7a) 

3d +5d (7b) (perform a page check 7a + 3) 

3c + 5c (7c) 

4e + the sum of the second set of near-rod readings from 6a (7d) 

4d + 6d (7e) (perform a page check 7d t- 3) 

4c + 6c(7f) 

7f-7c(7g) 



C-24 Basic Survey Computations 



FM 3-34.331 

























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Basic Survey Computations C-25 



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C-26 Basic Survey Computations 



FM 3-34.331 



Step 8. Apply the correction for C&R. Due to the short distance from the 
instrument to the near rod, no corrections are required to the near-rod 
readings. 

• Use the far-rod distance (4c + 10) as an argument to determine 
the second correction. TableC-1 shows correction factors for 
C&R according to the observed distance. Record the correction 
from TableC-1 in the C&R number 1 block (8b). 

• Use the far-rod distance (6c + 10) as an argument to determine 
the correction. Record the correction from TableC-1 in the C&R 
number 2 block (8c). 

• Correct the sum of the far-rod mean middle-wire readings for 
C&R. Algebraically add the sum of 8b and 8c to 7e. Since the 
correction is always negative, just subtract 8b and 8c from 7e 
(8d). 

• Algebraically add 8d and 7b. Record the sum with the sign (8e). 
8d is always negative. 

Table C-1. Correction Factors for C&R 



Distance (m) 


Correction to Rod (m) 


to 27.0 


-0.0 


27.1 to 46.8 


-0.1 


46.9 to 60.4 


-0.2 


60.5 to 71 .4 


-0.3 


71 .5 to 81.0 


-0.4 


81.1 to 89.5 


-0.5 


89.6 to 97.3 


-0.6 


97.4 to 104.5 


-0.7 



Step 9. Compute the C-value by dividing 8e by 7g. Truncate and record to 
four decimal places with the sign (9). 

NOTE : If the sum of the far-rod mean middle-wire readings (8d) is larger than the sum 
of the near-rod mean middle-wire readings (7b), the C-value is negative. 

Step 10. Compare the C-value with that allowed for the instrument. The 
allowable C-value in most instruments is +0.004. If the C-value is within 
specifications, no further computations are required. 
Step 11. Correct the C-value if it is not within the specifications. 

• The correction to the middle wire (in millimeters) is computed by 
multiplying the sum of the rod intervals of the last foresight 
(shown in 6c) by the C-value (shown in 9). Compute to one 
decimal place (round the answer) (11a). 



Basic Survey Computations C-27 



FM 3-34.331 



• The correction to the middle wire (11a) is added algebraically to 
the last foresight middle-wire rod reading (shown in 6a) toobtain 
the corrected rod reading. Compute to three decimal places 
(divide the correction by 1,000 to convert to meters before 
applying) (round the answer) (lib). 
Step 12. Initial the form (12). 

Step 13. Perform field adjustments. 

Step 14. Repeat steps 1 through 13 until the C-value is within specifications. 

Step 15. Give the recording form to the instrument operator once it has been 
determined that the instrument is within specifications. The instrument 
operator will check the form for completeness and the computations for 
correctness and initial the form (15). 



COMPUTATION OF A LEVEL LINE 



C-14. Computea level line on DA Form 1942. Refer toFigureC-16, pageC-30, 
when working steps 1 through 20 (the step numbers correspond to the 
numbered blocks). FigureC-17, pageC-31, shows a completed DA Form 1942. 
Data will be required from the field notes (DA Form 5820-R) shown in 
Figures C-18 through C-21, pages C-32 through C-35. 

Step 1. Complete the headings (1). 
Step 2. Record the name of the- 

• Beginning BM (2a). 

• BM whose elevation is being computed (2b). 

• Ending BM (2c). 
Step 3. Record the name of the- 

• Beginning BM for each section (3a). 

• Ending BM for each section (3b). 
Step 4. Record the name of the beginning BM (4). 

Step 5. Record the direction of the run (forward [F] or backward [B]) (5). 

Step 6. Abstract the length of the forward and backward runs per section 
from the level field notes. Record to the nearest 0.001 kilometer, in their 
respective directions (6). 

Step 7. Compute the length of the line by adding the shortest distance of 
each section of the level line (7a). Record the total length of the line (7b). 

Step 8. Compute the observed DE of the forward and backward runs per 
section from the level field notes. Record to four decimal places with the sign 
(in their respective running directions) (8). 

Step 9. Compute the DE between the forward and the backward runs per 
section. Record to four decimal places as an absolute value (no algebraic signs) (9). 



C-28 Basic Survey Computations 



FM 3-34.331 



Step 10. Determine the mean DE by computing the absolute mean of the 
forward and the backward DE. Give the mean DE the algebraic sign of the 
forward run. Record to four decimal places (round the answer) (10). 
Step 11. Record the known elevation of the beginning BM (11). 
Step 12. Record the known elevation of the ending BM (12). 

Step 13. Compute the observed elevation by algebraically adding the mean 
difference (shown in 10) and the elevation of the beginning BM (shown in 11). 
Record to four decimal places (13a). Compute each successive observed 
elevation by algebraically adding it to the preceding elevation and the 
respective section's mean DE. Record to four decimal places (13b). 

NOTE : The last entry will be the observed elevation of the ending BM. This entry must 
be compared to the fixed ending elevation. 

Step 14. Record the known elevation of the ending BM (from step 12) (14). 
Step 15. Compute the closure by subtracting the known elevation of the 
ending BM (shown in 14) from the computed observed elevation of the ending 
BM (shown in 13b). Record to four decimal places with the sign (15). 

Step 16. Compute the AE. Truncate and record to four decimal places (16). 
For third-order specifications, usethe following formula: 



AE = ±0.012 • JKm 
where— 
Km = length of line in kilometers (from 7b) 

Compare the AE (16) to the closure (shown in 15). If the numerical value of 

the closure is equal to or smaller than theAE, the level line meets third-order 

specifications. If it does not, there is no need to continue with the 

computations on DA Form 1942. 

Step 17. Compute the correction per kilometer. Divide the closure (shown in 

15) by the total length of the line (shown in 7b) and change the sign. Record to 

six decimal places with the sign (round the answer) (17). 

Step 18. Compute the correction for each section. Multiply the length of the 

line (shown in 7a) of each section by the correction per kilometer (shown in 

17). Record to four decimal places with the sign (round the answer) (18). 

NOTE : The correction to the final section must be equal to the closure (15), with the 
opposite sign. 

Step 19. Compute the adjusted elevation. Algebraically add the correction 
(shown in 18) to the observed elevation (shown in 13a) of each station. Record 
to four decimal places (round the answer) (19). 
Step 20. Sign and date the form (20). 



Basic Survey Computations C-29 



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3 



Basic Survey Computations C-33 



FM 3-34.331 











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3 



C-34 Basic Survey Computations 



FM 3-34.331 









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3 



Basic Survey Computations C-35 



Appendix D 

Survey Forms 

Surveyors use a variety of forms in the accomplishment of their duties. 
TableD-1 includes a list of forms (not addressed in this manual) used by 
surveyors. 



Table D-2. Survey Forms 



Number 


Title 


Date 


DA Form 1900 


Conversion of Mean Time to Sidereal Time 


1 February 1957 


DA Form 1901 


Conversion of Sidereal Time to Mean Time 


1 February 1957 


DA Form 1902 


Conversion of Mean Time to Apparent Time 


1 February 1957 


DA Form 1903 


Azimuth by Direction Method 


1 February 1957 


DA Form 1905 


Azimuth by Hour Angle Method 


1 February 1957 


DA Form 1907 


Azimuth by Altitude Method 


1 February 1957 


DA Form 1909 


Longitude by the Altitude of Stars Near the Prime 
Vertical 


1 October 1964 


DA Form 1911 


Altitude and Azimuth (Sin-Cos) 


1 February 1957 


DA Form 1914 


Computation of Base Line 


1 February 1957 


DA Form 1915 


Abstract of Levels and Computation of Inclination 
Corrections 


1 February 1957 


DA Form 1917 


List of Directions 


1 February 1957 


DA Form 1918 


Computation of Triangles 


1 February 1957 


DA Form 1921 


Reduction to Center 


1 February 1957 


DA Form 1922 


Position Computation, Order Triangulation 


1 October 1964 


(Logarithmic) 


DA Form 1924 


Inverse Position Computation 


1 February 1957 


DA Form 1925 


Quadrilateral Adjustment (Least Squares Method) 


1 February 1957 


DA Form 1927 


Latitude and Longitude Adjustment 


1 February 1957 


DA Form 1930 


Special Angle Computation 


1 February 1957 


DA Form 1931 


Traverse Computation (Geographic) 


1 February 1957 


DA Form 1935 


Grid Azimuth (t) and Grid Length 


1 February 1957 


DA Form 1936 


List of Directions, UTM Grid 


1 February 1957 


DA Form 1937 


Computation of Triangles (UTM Grid) 


1 February 1957 


DA Form 1939 


Reduction of Taped Distances 


1 February 1957 


DA Form 1941 


Grid and Declination Computations 


1 February 1957 


DA Form 1944 


Computation of Elevations and Refractions From 
Reciprocal Observations (Logarithmic) 


1 February 1957 


DA Form 1948 


Altimeter Leveling 


1 February 1957 



Survey Forms D-1 



FM 3-34.331 



Table D-2. Survey Forms (continued) 



Number 


Title 


Date 


DA Form 1949 


Corrected Altimeter Readings Prorated According to 
Time 


1 February 1957 


DA Form 1953 


Universal Polar Stereographic Transformations 


1 February 1957 


DA Form 1954 


Plane Coordinates From Geographic Coordinates on 
the Transverse Mercator Projection (Calculating 
Machine Computation) 


1 February 1957 


DA Form 1955 


Geographic Coordinates From Transverse Mercator 
Grid Coordinates (Calculating Machine Method) 


1 February 1957 


DA Form 1956 


Plane Coordinates From Geographic Coordinates on 
the Lambert Projection (Calculating Machine 
Computation) 


1 February 1957 


DA Form 1 957 


Geographic Coordinates From Lambert Grid 
Coordinates (Calculating Machine Computation) 


1 February 1957 


DA Form 1959 


Description or Recovery of Horizontal Control Station 


1 October 1964 


DA Form 2839 


Latitude From Zenith Distance of Polaris 


1 October 1 964 


DA Form 2847 


Comparison of Chronometer and Radio Signals 


1 October 1964 


DA Form 2850 


Astronomic Results 


1 October 1964 


DA Form 2854 


Electronic Distance Measurement Summary 


1 October 1 964 


DA Form 2855 


Geodimeter (Model 4) Observations and Computations 


1 October 1964 


DA Form 2856 


Field Sheet, Tellurometer Data Entries (MRA3 MK11) 


1 October 1964 


DA Form 2857 


Field Sheet, Micro-Chain Data Entries 


1 October 1964 


DA Form 4253 


Horizontal Direction or Angle Book 


June 1974 


DA Form 4446 


Level, Transit, and General Survey Record 


November 1975 


DA Form 4648 


Station Description Book 


September 1977 


DA Form 581 8-R 


General Survey Notes (LRA) 


August 1989 



D-2 Survey Forms 



Glossary 



- 


perspective to 


z 


angle(s) 


o 


degree(s) 


a 


azimuth of line 


a 


angle 


K 


correction for the earth's curvature 


i 


sum 


/ 


minute(s) 


// 


second (s) 


A 


delta 


AE 


delta easting 


AN 


delta northing 


♦ 


latitude 


<J> 


phi 


hi 


elevation of the occupied station 


X 


longitude 


e 


Theta 


p 


symbol for rho- radius of curvature 


s 


grid distance 


o 


sigma 


X 


tau 


5 


mean observed zenith distance 


ID 


one dimensional 


1DRMS 


1-deviation root-mean-square 


1LT 


first lieutenant 


1SG 


first sergeant 


2D 


two dimensional 


2DRMS 


2-deviation root-mean-square 


3D 


three dimensional 


3DRMS 


3-deviation root-mean-square 



A/M angle measure 

AAF Army airfield 

AAL additional authorizations list 

AC alternating current 



Glossary-1 



FM 3-34.331 



accuracy 



actual error 

ADA 

adj 

adjust 

adjusted position 



AE 

AEC 

aeronautical beacon 



AG 

AH 

air-navigation facility 



airport elevation 
airport lighting 



the degree of conformity with a standard or the degree of 
perfection attained in a measurement; accuracy relates to the 
quality of a result and is distinguished from precision, which 
relates to the quality of the operation used to obtain the result 

the difference between the accepted value and the measured value 
of a physical quantity 

air-defense artillery 

adjusted 

adjustment 

an adjusted value for the horizontal or vertical position of a survey 
station, in which discrepancies due to errors in the observed data 
are removed, that forms a coordinated and correlated system of 
stations 

allowable error 

angular error of closure 

a visual N AVAI D displaying flashes of white and/or colored light 
to indicate the location of an airport, a heliport, a landmark, a 
certain point of a federal airway in mountainous terrain, or an 
obstruction 

Adjutant General 

ampere-hour 

any facility used in, available for use in, or designed for use in the 
aid of air navigation (this includes landing areas; lights; any 
apparatus or equipment used for disseminating weather 
information, signaling, radio-directional finding, or radio or other 
electrical communication; and any other structure or mechanism 
having a similar purpose of guiding or controlling the flight, the 
landing, or the takeoff of aircraft) 

the highest point of an airport's usable runways measured in feet 
from the M SL 

various lighting aids installed on airports. These aids can include 

1) airport rotating beacons— a visual N AVAI D that is operated at 
many airports. At civil airports, alternate white and green flashes 
indicate the location of the airport. At military airfields, the 
beacon is differentiated by dual peak (two quick) white flashes 
between the green flashes; 

2) approach-light systems (ALSs)— an airport lighting facility 
which provides visual guidance to landing aircraft by radiating 
light beams in a directional pattern by which the pilot aligns the 
aircraft with the extended runway centerli neon hisfinal approach 
for landing. A number of ALS configurations exist, both with and 
without sequenced flashing lights. One system, the 
omnidirectional ALS (ODALS), consists of seven omnidirectional 
flashing lights located in the approach area of a nonprecision 
approach. Five of the lights are located on the extended runway 
centerli ne and the other two lights are located one on each side of 
the runway threshold; 



2-Glossary 



FM 3-34.331 



airport reference point 



airport surveillance 
radar 



air-route surveillance 
radar 



AISI 

ALP 

ALS 

altimeter 

altitude 

ambiguity resolution 



3) REILs— two synchronized flashing lights, one on each side of 
the runway threshold, provide rapid and positive identification of 
the approach end of a runway; 

4) visual -approach slope indicators (VASI)— an airport lighting 
facility providing vertical visual-approach slope guidance to 
aircraft during the approach for landing by radiating a directional 
pattern of high-intensity, red and white, focused light beams, 
which indicate to the pilot if he is above, below, or on the glide 
path. The term VASI also has a generic connotation for a tricolor- 
approach slope indicator consisting of a single light unit projecting 
a three-color, visual-approach path into the final approach area of 
the runway served by the system; 

5) pulse-light approach-slope indicators (PLASI )— a VASI , 
normally consisting of a single light unit projecting a pulsating 
two-color, visual-approach path into the final approach area of the 
runway served by the system; and 

6) precision approach-path indicators (PAPI)— a VASI, consisting 
of a single row of two or four light units, usually installed on the 
left side of the runway served by the system 

the position of the approximate center of mass of all usable 
runways. This point is not strictly the center of mass of runways, 
sincethe runway width, thickness, or material is not considered in 
the computation. An ARP is not monumented; therefore, it is not 
recoverable on the ground 

approach control radar that is used to detect and display an 
aircraft's position in the terminal area. The ASR provides range 
and azimuth information but does not provide elevation data 
(coverage of the ASR can extend up to 60 nautical miles) 

air-route traffic control center (ARTCC) radar used primarily to 
detect and display an aircraft's position while en route between 
terminal areas (coverage of the ARSR can extend up to 200 
nautical miles) 

automated integrated survey instrument 

airport location point 

approach-light system 

an aneroid barometer that is used for the measurement of 
approximate elevations or approximate differences of elevation 

the vertical angle that is measured between the plane of the 
observer's true horizon and a line to the object 

with carrier-phase observations, the number of carrier-phase 
cycles between the receiver and the satellite is generally unknown 
and is referred to as the ambiguity and is an integer number. 
Single and double differences are also affected by ambiguities, 
which are formed by a linear combination of carrier-phase integer 
ambiguities (for example, a single or double differenced 
ambiguity). Where the integer ambiguities are unknown, they 
may be estimated by processing software. I n some cases, these 
real-valued estimates may be used to determine the correct 
integer values, which are then held fixed. A float solution is derived 
when the real-valued estimates are used, rather than the integers 



Glossary-3 



FM 3-34.331 



ang 

ant 

AO 

AOC 

AP 

APFT 

approx 

Apr 

apron 



AR 

ARP 

ARSR 

ARTCC 

ARTEP 

AS 

ASCII 

ASPRS 

ASR 

astronomical latitude 



astronomical longitude 



ATC 

Aug 

az 

azimuth 



azimuth mark 



angle 

antenna 

area of operation 

airport obstruction chart 

airport plan 

Army physical fitness test 

approximate 

April 

a defined area on an airport or heliport intended to accommodate 
aircraft for purposes of loading and unloading passengers or cargo, 
refueling, parking, or maintenance (seaplanes use a ramp for 
access from the water to the apron) 

Army regulation 

airport reference point 

air-route surveillance radar 

air-route traffic control center 

ArmyTraining and Evaluation Program 

antispoofing 

American Standard Code for I nformation I nterchange 

American Society of Photogrammetry and Remote Sensing 

airport surveillance radar 

the angle between the plumb line and the plane of the celestial 
equator; also defined as the angle between the plane of the horizon 
and the axis of rotation of the earth. Astronomical latitude applies 
only to positions on the earth and is reckoned from the astronomic 
equator (0°), north and south through 90°. Astronomical latitude 
results directly from observations of celestial bodies, which are 
uncorrected for deflection of the vertical 

the angle between the plane of the celestial meridian and the 
plane of an initial meridian that is arbitrarily chosen. 
Astronomical longitude results directly from observations on 
celestial bodies, uncorrected for deflection of the vertical 

air traffic control 

August 

azimuth 

the direction of one object from another, usually expressed as an 
angle in degrees relative to true north (azimuths are usually 
measured in the clockwise direction, thus an azimuth of 90° 
indicates that the second object is due east of the first) 

the azimuth to a marked point or adjacent station that is visible 
from an occupied station, which is determined for use in 
dependent surveys 



4-Glossary 



FM 3-34.331 



backsight 



BAQ 
base network 

baseline 



basic control 

BC 

BCM 

bearing 

benchmark 



BEQ 

bde 

BDE 

Bll 

blast pad 

BM 

bn 

broadcast ephemeris 



bs 
btry 



backward 

in traversing, a backsight is a sight on a previously established 
traverse or triangulation station, which is not the closing sight on 
the traverse; in leveling, a backsight is a reading on a rod that is 
held on a point whose elevation has been previously determined 
and is not the closing sight of a level line 

basic allowance for quarters 

a small network of geometric figures that is used to expand from a 
baseline to a line of the main scheme of a triangulation network 

a surveyed line that is established with more than usual care, to 
which surveys are referred for coordination and correlation; in 
GPS baseline reduction, geodetic parameters are estimated at one 
station relative to another, with the receivers at both sites 
observing common satellites simultaneously 

horizontal and vertical control of third- or higher-order accuracy 
(determined in the field and permanently marked or 
monumented) that is required to control further surveys 

basic control 

basic-control marker 

the direction of one object from another, usually expressed as an 
angle in degrees relative to a specific primary direction (bearings 
differ from azimuths in that bearing values do not exceed 90°) 

a relatively permanent object, natural or artificial, bearing a 
marked point whose elevation above or below an adopted datum is 
known; usually designated as a BM, such a mark is sometimes 
further qualified as a PBM or as a temporary BM (TBM) 

bachelor enlisted quarters 

brigade 

backward difference in elevation 

basic issue items 

a specially prepared surface that is placed adjacent to the ends of 
runways to eliminate the erosive effect of the high wind forces 
produced by airplanes at the beginning of their takeoff rolls 

benchmark 

battalion 

the predicted satellite position in its orbit as a function of time 
computed from the ephemeris parameters contained in the 
navigation message broadcast on both the LI and L2 carrier 
waves 

backsight 

battery 



C 2 command and control 
C Celsius 
C/A-code coarse-acquisition code 



Glossary-5 



FM 3-34.331 



CAD 
cadastral survey 



CADD 
carrier phase 

C -check 

CDC 

celestial equator 



celestial meridian 



celestial pole 



celestial sphere 



central meridian 



CEOI 

CEP 

CESI 

C -factor 

chron 

chronometer 

CID 
circle position 

circuit closure 



computer-aided design 

a survey relating to land boundaries and subdivisions, which is 
made to create units suitable for the transfer of or to define the 
limitations of a title; surveys of the public lands of the US, 
including retracement surveys for the identification of and 
resurveys for the restoration of property lines; and for 
corresponding surveys outside the public lands, although such 
surveys are usually termed land surveys 

computer-aided design and drafting 

the phase (as measured at the antenna phase center of a GPS 
receiver) of two si nusoidal radio signals (the two carriers) that are 
continuously emitted by each GPS satellite 

colli mat ion test for leveling 

consecutive Doppler counts 

a great circle on the celestial sphere on which any point is 
equidistant from the celestial poles (the plane of the earth's 
equator, if extended, would coincide with that of the celestial 
equator) 

a vertical circle (the plane of which is perpendicular to the 
celestial equator) passing through both celestial poles 

a reference point located at the point of intersection of an 
indefinite extension of the earth's axis of rotation and the 
apparent celestial sphere 

an imaginary sphere of infinite radius, with the earth as the 
center, that rotates from east to west on a prolongation of the 
earth's axis 

the longitude of the horizontal center of a coordinate system (this 
longitude value is often the longitude origin of the coordinate 
system); in the case of the transverse Mercator projection, theCM 
is the great circle/geodesic at which the projection surface (the 
cylinder) touches or is tangent to the earth 

communications-electronics operation instructions 

circular error probable 

communications-electronics standing instruction 

collimation error; error of the sighting of the level 

chronometer 

a portable timekeeper with compensated balance, which is capable 
of showing time with extreme precision and accuracy 

continuously integrated Doppler 

a prescribed setting (reading) of the horizontal circle of a direction 
theodolite, which is used for observing the initial station of a 
series of stations 

in leveling, it is the amount by which the algebraic sum of the 
measured differences of elevation around a circuit fails to equal 
zero 



6-Glossary 



FM 3-34.331 



circumpolar star 



cl 

C/L 

clearway 



cm 

CM 

COEI 

col I imation 



comm 

comp 

compass locator 



control 



control survey 

CONUS 
coordinate system 



coordinates 



coords 



a star in any given latitude that never goes below the horizon; 
hence, its polar distance must be less than the given latitude; in 
astronomy, only those stars with a polar distance of less than 10° 
are considered in practical problems 

closure 

centerline 

an area beyond the takeoff runway that is under the control of 

airport authorities where terrain or fixed obstacles may not 

extend above specified limits (these areas may be required for 

turbine-powered operations and the size and upward slope of the 

clearway will differ depending on when the aircraft was certified) 

centimeter(s) 

central meridian 

components of end item 

the line of sight or aiming line of an instrument when coincident 

with the physical alignment of the instrument; thus, a col I imation 

error is the angle between the line of col I imation (line of sight) of a 

telescope and the col I imation axis of the instrument 

communication 

computer 

a low-power, low- or medium-frequency (L/MF) NDB that is 
installed at the site of the outer or middle marker (MM) of an ILS 
(it can be used for navigation at distances of about 15 miles or as 
authorized in the approach procedure) 

the coordinated and correlated dimensional data, which are used 
in geodesy and cartography to determine the positions and 
elevations of points on the earth's surface or on a cartographic 
representation of that surface; a collective term for a system of 
marks or objects on the earth or on a map or a photograph whose 
positions or elevations, or both, have been or will be determined 

a survey that provides positions (horizontal or vertical) of points to 
which supplementary surveys are adjusted 

continental United States 

an exact definition of a system of mathematics and geodetic 
constants that defines how a specific geographic location is 
converted to a set of two or three numbers (for example, an X- and 
Y-value [and possibly a Z-value]); in the cartographic context, 
most coordinate systems are Cartesian (the axes are orthogonal 
[perpendicular to each other]) and the units are the same on all 
axes; the principle exception to this is the spherical coordinate 
system of latitudes and longitudes 

linear and/or angular quantities, which designate the position of a 
point in relation to a given reference frame; there are two general 
divisions of coordinates used in surveying— polar and rectangular; 
these may be further subdivided into three classes— plane 
coordinates, spherical coordinates, and space coordi nates 

coordinates 



Glossary-7 



FM 3-34.331 



Corps Conversion 



Corpscon 

corr 

CORS 

cos 

CPT 

C&R 

CTT 

cycle slips 



a software program that converts horizontal coordinates to and 

from geographic, state-plane, and UTM systems on the NAD 27 

and the NAD 83 and converts vertical coordinates on the 

NGVD 29 and the NAVD 88 

Corps Conversion 

correction 

continuously operating reference station 

cosine 

captain 

curvature and refraction 

common training task 

cycle slips occur when there are breaks in the continuity of signal 
in a satellite- receiver pair. Data sampling requires the choosing of 
the sampling rate and the starting and finishing epochs for the 
observations. Data editing is required for cycle slips and for data 
sampling 



D ratio of side/sine 

DA Department of the Army 

datum the combination of an ellipsoid, that specifies the size and shape of 
the earth, and a base point from which the latitude and longitude 
of all other points are referenced. Before satellites, lasers, and 
computers, establishing precise values for these points was 
impossible. More recently, many datums have been established 
and substantial amounts of data collected based on each. Data 
based on one datum will not necessarily overlay data based on 
another datum. A geodetic datum is a reference surface consisting 
of five quantities: the latitude and longitude of an initial point, the 
azimuth and distance of a line from this point, and the parameters 
of the reference ellipsoid. It forms the basis for the computation of 
horizontal-control surveys in which the curvature of the earth is 
considered. A leveling datum is a level surface to which elevations 
are referred (usually, but not always, theMSL) 

DD Department of Defense 

dE difference in easting 

DE difference in elevation 

declination in a system of polar or spherical coordinates, the angle at the 
origin between a line to a point and the equatorial plane, 
measured in a plane perpendicular to the equatorial plane; the arc 
between the equator and the point measured on a great circle, 
which is perpendicular to the equator; as it relates to astronomy, 
the angular distance to a body on the celestial sphere that is 
measured north or south through 90° from the celestial equator 
along the hour circle of the body. Comparable to latitude on the 
terrestrial sphere and often used as a shortened term for magnetic 
declination 



8-Glossary 



FM 3-34.331 



deflection of the 
vertical 



deg 

det 

dev 

DGPS 

dH 

diff 

differencing 



dir 
direct leveling 



direct reading 



direction finder 

direction instrument 
theodolite 



dist 
distance angle 



distance measuring 
equipment 



the angular difference, at any place, between the upward direction 
of a plumb line (the vertical) and the perpendicular (the normal) to 
the reference spheroid. This difference seldom exceeds 30 seconds 
and is often expressed in two components— meridian and prime 
vertical 

degree(s) 

detachment 

deviation 

differential global-positioning system 

difference in the horizontal aim 

difference 

nondifferencing (one-way phase) is the measured carrier phase 
between one satellite and one receiver. Single differencing (first 
difference) is the difference between one-way measurements 
recorded at two receivers (for example, two receivers 
simultaneously observing a common satellite and differencing the 
recorded measurements). Double differencing (second difference) 
is the difference between two single differences (for example, two 
stations observing two satellites, forming differences between the 
site pair and the satellite pair). Triple differencing (double 
difference rate/epoch differences) is the differencing of double 
differences between consecutive epochs 

direction 

the determination of DEs by the means of a continuous series of 
short horizontal lines. Vertical distances from these lines to 
adjacent ground marks are determined by direct observations on 
graduated rods with a leveling instrument equipped with a spirit 
level 

the reading of the horizontal or vertical circle of a theodolite or 
engineer transit with the telescope in the direct position. In field 
notes, a direct reading is indicated with a letter D preceding the 
observed value 

a radio receiver equipped with a directional sensing antenna used 
to take bearings on a radio transmitter 

a theodolite in which the graduated horizontal circle remains 
freed during a series of observations. The telescope is pointed on a 
number of signals or objects in succession and the direction of each 
is read on the circle (usually by means of micrometer microscopes). 
Direction instrument theodolites are used almost exclusively in 
first- and second-order triangulation 

distance 

an angle in a triangle that is opposite the side which is used as a 

base in the solution of the triangle or a side whose length is to be 

computed 

equipment that is (airborne or ground) used to measure (in 

nautical miles) the slant-range distance of an aircraft from the 

DME NAVAID 



DIVARTY division artillery 



Glossary-9 



FM 3-34.331 



DMA Defense M appi ng Agency 

DME distance measuring equipment 

DMS Defense Mapping School 

dN difference in northing 

DOD Department of Defense 

DOP dilution of precision 

DPW Directorate of Public Works 

D/R di rect/reverse 

DRU data recording unit 

dsplcd displaced 

DT displaced threshold 

dV difference in the vertical aim 



E 

EAC 

EC 

ECEF 

ecliptic 

EDM 

EDME 

Ee 

elev 

elevation 



ell 
ellipsoid 



ellipsoid height 



east 

echelons above corps 

error of closure 

earth centered earth fixed 

the great circle of the celestial sphere that is the apparent path of 
the sun among the stars or of the earth as seen from the sun. It is 
inclined to the celestial equator at an angle of about 23°27' 

electronic distance measurement 

electronic distance measuring equipment 

error in easting 

elevation 

the vertical distance from a datum, usually the MSL, to a point or 
object on the earth's surface (not to be confused with altitude, 
which refers to points or objects above the earth's surface) 

ellipsoidal 

the mathematical shape that best descri bes the shape of the earth 
and yet is relatively simple to deal with mathematically. 
Ellipsoids are defined with two numbers. First, the equatorial 
radius isspecified (also referred to as the semi major axis). Second, 
one of the following three numbers is given, the polar radius (also 
known as the semi mi nor axis), the eccentricity, or the flattening. 
Given the equatorial radius and any one of the three secondary 
values, the remaining secondary values can be computed. A 
specific determination of the size of the earth is often referred to 
as an ellipsoid. For example, the phrase "Clarke ellipsoid of 1866" 
is frequently used to refer to the measurements of the size of the 
earth made by Clarke in 1866 

the height of an object above the reference ellipsoid in use. This 
term is generally used to qualify an elevation as being measured 
from the ellipsoid as opposed tothegeoid. GPS systems calculate 
ellipsoidal height. The geoid height at that location must be 
subtracted to obtain what is commonly referred to as the elevation 



10-Glossary 



FM 3-34.331 



elongation 

EM 

en 

En 

eng 

engr 

EOR 

ephemeristime 

equation of time 

equinox 
error 



error of closure 



esc 



the point in the apparent movement of a circumpolar star when 
the star reaches the extreme position east or west of the meridian 

engineer manual 

engineer 

error in northing 

engineer 

engineer 

end of runway 

a uniform measure of time that is defined by the laws of dynamics 

and determined in principle from the orbital motions of the 

planets, specifically in the orbital motion of the earth 

the algebraic difference in hour anglebetween apparent solar time 
and mean solar time (usually labeled plus or minus), as it is to be 
applied to mean solar time to obtain apparent solar time 

one of the two poi nts of i ntersection of the eel i ptic and the celesti al 
equator, which is occupied by the sun when its declination is 0° 

the difference between an observed and true value; a class of small 
inaccuracies due to imperfections in equipment or techniques, 
surrounding conditions, or human limitations; not to be confused 
with blunders or mistakes 

the amount by which a quantity obtained by a series of related 
measurements differs from the true or fixed value of the same 
quantity. These include errors of closure for thefollowing: 

Angle. The amount by which the actual sum of a series of angles 
fails to equal the theoretically exact value of that sum. 

Azimuth. The amount by which two values of the azimuth of a 
line, derived by different surveys or along different routes, fail to 
be exactly equal to each other. 

Horizon. The amount by which the sum of a series of adjacent 
measured horizontal angles around a point fails to equal exactly 
360°. Measurement of the last angle of the series is called closing 
the horizon (sometimes called closure of horizon). 

Leveling. The amount by which two values of the elevation of the 
same BM , derived by different surveys or through different survey 
routes or by independent observations, fail to be exactly equal to 
each other 

Loop. The error in the closure of a survey on itself. 

Triangle. The amount by which the sum of the three observed 
angles of a triangle fails to equal exactly 180° plus the spherical 
excess of the triangle. 

Traverse. The amount by which a value of the position of a 
traverse station, as obtained by computation through a traverse, 
fails to agree with another value of the same station as 
determined by a different set of observations or routes of survey 

escape 



Glossary-1 1 



FM 3-34.331 



f 

F 

FA 

FAA 

FAA405 

FAO 

FAR 

FAR-77 

FDE 

Feb 

FEBA 

FED 

FGCC 

FGCS 

final-approach course 

fixed elevation 



FM 

FM 

FO 

foresight 



FOUO 

FRAGO 

frequency 

FRNP 

fs 

FS 

FSCOORD 

ft 



forward 

Fahrenheit 

field artillery 

Federal Aviation Administration 

Federal Aviation Administration Publication 405 

finance and accounting office 

Federal Aviation Regulation 

Federal Aviation Regulation, Part 77 

forward difference in elevation 

February 

forward edge of the battle area 

Facilities Engineering Division 

Federal Geodetic Control Committee 

Federal Geodetic Control Subcommittee 

a straight-line extension of a localizer, a final approach radial/ 
bearing, or a runway centerline, all without regard to distance 

an elevation that has been adopted (either as a result of tide 
observations or previous adjustment of spirit leveling) and is held 
at its accepted value in any subsequent adjustment 

field manual 

frequency modulated 

forward observer 

an observation of the distance and direction to the next 
instrument station. I n traversing, a foresite is a point set ahead to 
be used for reference when resetting the transit or line or when 
verifying the alignment. In leveling, a foresite is the reading on a 
rod that is held at a point whose elevation is to be determined 

for official use only 

fragmentary order 

the number of complete cycles per second existing in any form of 
wave motion 

Federal Radio Navigation Plan 

foresight 

fire support 

fire-support coordinator 

feet, foot 



G2 Assistant Chief of Staff, G2 (Intelligence) 

G3 Assistant Chief of Staff, G3 (Operations and Plans) 



12-Glossary 



FM 3-34.331 



GCA 

GDOP 

geod 

geodesy 



geodetic control 



geodetic latitude 



geodetic leveling 



geodetic longitude 



geodetic reference 
system 



geodetic survey 

geographic coordinates 

geoid 

GEOID93 

GEOID96 

GEOID99 

geoid height 



ground-controlled approach 

geometric dilution of precision 

geodetic 

a branch of applied mathematics concerned with the 
determination of the size and shape of the earth (geoid). Direct 
measurements (triangulation, leveling, and gravimetric 
observations) determine the exact location of points on the earth's 
surface and its external gravitational field 

a system of horizontal and/or vertical control stations that have 
been established and adjusted by geodetic methods and in which 
the shape and size of the earth (geoid) have been considered in 
position computations 

the angle at which the normal (at a point on the reference 
spheroid) forms with the plane of the geodetic equator. Geodetic 
latitudes are reckoned from the equator, but in the horizontal- 
control survey of the US, they are computed from the latitude of 
station Meades Ranch as prescribed in NAD 27 

spirit leveling of a high order of accuracy, usually extended over 
large areas, to furnish accurate vertical control as a basis for the 
control in the vertical dimension for all surveying and mapping 
operations 

the angle between the plane of the geodetic meridian and the 
plane of an initial meridian. A geodetic longitude can be measured 
by the angle at the pole of rotation of the reference spheroid 
between the local and initial meridians or by the arc of the 
geodetic equator intercepted by those meridians. In the US, 
geodetic longitudes are numbered from the meridian of 
Greenwich, but are computed from the meridian of station Meades 
Ranch as prescribed in NAD 27. A geodetic longitude differs from 
the corresponding astronomical longitude by the amount of the 
prime vertical component of the local deflection of the vertical 
divided by the cosine of the latitude 

the technical name for a datum. The combination of an ellipsoid, 
which specifies the size and shape of the earth, and a base point 
from which the latitude and longitude of all other points are 
referenced 

a survey of a large land area in which corrections are made for the 
curvature of the earth's surface 

an inclusive term that is generally used todesignate both geodetic 
and astronomical coordinates 

the surface within or around the earth that is everywhere normal 
to the direction of gravity and coincides with MSL in the oceans 

Geoid reference model 1993 

Geoid reference model 1996 

Geoid reference model 1999 

the height of the geoid above the ellipsoid in use (this usually 
refers to the height of the geoid above the WGS-84 ellipsoid upon 
which GPS is based) 



Glossary-13 



FM 3-34.331 



GEOREF 

GIS 

global positioning 
system 



GPS 

GPS-S 

gravi meter 



gravitation 



gravity 



gr ou nd-control I ed 
approach 

GRS 

GRS80 

GS 

GSI 

GSR 

GySgt 



geographic reference 

geographic information system 

a system (developed by the US military) based on satellites and 
sophisticated receivers that are capable of accurately measuring 
the geodetic location of a receiver at any place in the world and is 
widely used in surveying and navigational situations 

global positioning system 

global positioning system-survey 

a weighing device or instrument of sufficient sensitivity that is 
used to register variations in the weight of a constant mass when 
the mass is moved from place to place on the earth and thereby is 
subjected to the influence of gravity at those places 

the acceleration produced by the mutual attraction of two masses, 
directed along the line joining their centers of mass, and of 
magnitude inversely proportional to the square of the distance 
between the two centers of mass 

viewed from a frame of reference freed in the earth (acceleration 
imparted by the earth to a mass), which is rotating the earth. 
Since the earth is rotating, the acceleration observed as gravity is 
the resultant of the acceleration of gravitation and the centrifugal 
acceleration arising from this rotation and the use of an 
earthbound rotating frame of reference. 

a radar approach system operated from the ground by ATC 
personnel transmitting instructions to the pilot by radio (the 
approach may be conducted with ASR and/or PAR) 

geodetic reference system 

Geodetic Reference System of 1980 

general support 

glide-slope indicator 

ground-surveillance radar 

gunnery sergeant 



h 

h 

H 

HARN 

H Dist 

HDOP 

height of instrument 



Hg 



ellipsoidal height 

hour(s) 

orthometric height 

high-accuracy reference network 

horizontal distance 

horizontal dilution of precision 

in spirit leveling, it is the height of the line of sight of a leveling 
instrument above the adopted datum. In stadia surveying, it is the 
height of the center of the telescope (horizontal axis) of the transit 
or telescopic alidade above the ground or station mark. I n 
trigonometric leveling, it is the height of the center of the 
theodolite (horizontal axis) above the ground or station mark 

the symbol for the element mercury 



14-Glossary 



FM 3-34.331 



HHB 

HHC 

HI 

horizontal control 

horizontal refraction 



HQ 

ht 

HT 



headquarters and headquarters battery 

headquarters and headquarters company 

height of instrument 

a control point that determines horizontal positions only, with 
respect to parallels and meridians or toother lines of reference 

a natural error in surveying, which is the result of the horizontal 
bending of light rays between a target and an observing 
instrument. This error is usually caused by the differences in 
density of the air along the path of the light rays, resulting from 
temperature variations 

headquarters 

height 

height of the observed target 



IEW 

IFR 

I ID 

ILS 

IM 

imaginary surface 



in 

INS 

inst 

instr 

instrument landing 
system 

instrument runway 

int 

intersection method 



intelligence and electronic warfare 

instrument flight rules 

intermittently integrated Doppler 

instrument landing system 

inner marker 

any surface that is defined in FAR-77, subpart C. A specified 
surface is an imaginary surface (other than a supplemental 
surface) that is designated by appropriate FAA authorities for 
defining obstructions. This surface may or may not be the surface 
specified in FAR-77 for existing approach minimums. A 
supplemental surface is an imaginary surface designated by 
appropriate FAA authorities. A supplemental surface will 
normally lie below a specified surface and is intended to provide 
additional obstruction information. An object that penetrates a 
supplemental surface only is a supplemental obstruction 

inch(es) 

inertial navigation system 

instrument 

instrument 

a precision instrument approach system that normally consists of 
electronic components and visual aids (for example, localizer, glide 
slope, outer marker (OM), MM, and approach lights) 

a runway equipped with electronic and visual NAVAI Ds 

initials 

a method of determining the horizontal position of a point by 
observations from two or more points of known position, thus 
measuring directions that intersect at the station being located. A 
station whose horizontal position is located by intersection is 
known as an intersection station 



Glossary-15 



FM 3-34.331 



ionospheric correction 



isogonic chart 

isogonic line 

ISVT 



the ionosphere causes a delay in the propagation of a GPS signal 
that can be estimated with 50 percent accuracy using any 
recognized atmospheric model. On baselines shorter than 
20 kilometers, it is mostly eliminated by relative positioning. For 
greater accuracy, it can be mostly eliminated by dual frequency 
observations and processing 

a chart that features a system of isogonic lines, each for a different 
value of the magnetic declination 

a line drawn on a map or chart joining points of equal magnetic 
variation 

initial site-visitation trip 



J AG J udge Advocate General 

J an J anuary 

K a scale factor used to convert a measured distance to a grid 
distance 

K* a scale factor used to reduce a grid distance 

KE correction to easting 

km kilometer(s) 

KN correction to northing 



landing direction 
indicator 

I at 

latitude 



L-band 

LEC 

level datum 



a device that visually indicates the direction in which landings 
and takeoffs should be made 

latitude 

the north/south component of the spherical coordinate system 
most widely used to record geodetic locations. Originally, when the 
earth was thought to be spherical, a degree of latitude represented 
one degree of arc on the surface of the earth, which is referenced to 
the center of the earth. Now that it is known that the earth is 
ellipsoidal in shape, there are several types of latitude. The usual 
definition of latitude is the angle a line, perpendicular to the 
surface of the ellipsoid, forms with the plane of the equator. This 
is also referred to as the geographic latitude or geodetic latitude. 
Whenever the unqualified term latitude is used, it is generally 
accepted that it refers to the geographic latitude. Normal 
conventions dictate that north latitudes be given in degrees where 
positive numbers indicate north latitudes and negative numbers 
indicate south latitudes 

frequency used by SVs to exchange information 

linear error of closure 

a level surface to which elevations are referred. The generally 
adopted level datum for leveling in the US is the MSL. For local 
surveys, an arbitrary level datum is often adopted and defined in 
terms of an assumed elevation for some physical BM 



16-Glossary 



FM 3-34.331 



level net 
line of sight 



L/MF 
localizer 



localizer back course 



localizer -type 
directional aid 



Ion 

long 

longitude 



long-range navigation 



LOP 

LORAN 

LRA 

LTC 



Lines of spirit leveling connected together to form a system of 
loops or circuits extending over an area 

the straight line between two points (this line is in the direction of 
a great circle but does not follow the curvature of the earth); also, 
the line extending from an instrument along which distant objects 
are seen when viewed with a telescope or another sighting device 

low or medium frequency 

the component of an I LS that provides course guidance to the 
runway 

the course line defined by the localizer signal along the extended 
runway centerline in the opposite direction to the normal localizer 
approach course (front course) 

a NAVAID used for nonprecision instrument approaches with 
utility and accuracy comparable to a localizer; however, it is not 
part of a complete ILS and is not aligned with the runway 

longitude 

longitude 

the east/west component of the spherical coordinate system most 
widely used to record geodetic locations. Lines of longitude are 
great circles/geodesies, which pass through the north and south 
pole, and intersect the equator. All lines of longitude proceed in a 
true north/south direction. The imaginary lines of longitude are 
assigned values that represent, in degrees of arc, the distance of 
the line from the prime meridian (the line of longitude that passes 
through Greenwich, England, is the most common prime meridian 
in use today) 

an electronic navigation system by which hyperbolic LOPs are 
determined by measuring the difference in the time of reception of 
synchronized pulse signals from two fixed transmitters. The long- 
range navigation (LORAN) A operates in the 1750- to 1950- 
kilohertz frequency band. The LORAN C and D operate in the 
100- to 110-kilohertz frequency band 

line of position 

long-range navigation 

local reproduction authorized 

lieutenant colonel 



MACOM 

mag 

main-scheme station 

Mar 



meter(s) 

minute(s) 

major Army command 

magnetic 

a station through which the basic survey computations are 
carried, also called a principal station 

March 



Glossary-17 



FM 3-34.331 



marker beacon 



mean sea level 



meas 

meridian 

met 

MET 

MFR 

MGRS 

mi 

micro 

MID E 

MID N 

mil 

min 
minimum 



missed approach 

MLRS 

MLS 

mm 



an electronic NAVAI D transmitting a 75-megahertz vertical-fan 

or bone-shaped radiation pattern. Marker beacons are identified 

by their modulation frequency and keying code and, when received 

by compatible airborne equipment, indicate to the pilot (both 

aurally and visually) that he is passing over the facility. Marker 

beacons include the foil owing: 

Basic-control marker (BCM). When installed, this normally 

indicates the localizer basic-control final-approach fix where 

approach descent is commenced. 

Inner marker (IM). A marker beacon (used with an ILS 

category- 1 1 precision approach) that is located between the MM 

and the end of the ILS runway. It also marks progress during an 

ILS category-l II approach. The I M is usually located at the point 

of decision height for I LS category-l I approaches. 

MM. A marker beacon that defines a point along the glide slope of 

an I LS, usually located at or near the point of decision height for 

ILS category-l approaches. 

OM. A marker beacon that is at or near the glide-slope intercept 

altitude of an I LS approach. The OM is normally located 4 to 7 

miles from the runway threshold on the extended centerlineof the 

runway 

the mean surface-water level that was determined by averaging 
heights at all stages of the tide over a 19-year period (often used as 
a reference for general leveling operations) 

measurement 

in a cartographic/geodetic context, a meridian is a line of longitude 

meteorological 

missile escort team 

memorandum for record 

military grid-reference system 

mile(s) 

micrometer 

middle easting 

middle northing 

a unit of angular measurement that is equal to 1/6400 of 360° and 
used especially in FA 

minute(s) 

weather condition requirements that are established for a 
particular operation or type of operation (for example, instrument 
flight rules (I FR) takeoff or landing, alternate airport for I FR 
flight plans, or visual flight rules (VFR) flight) 

a maneuver that is conducted by a pilot when an instrument 
approach cannot be completed to landing 

multiple-launch rocket system 

microwave landing system 

millimeter(s) 



18-Glossary 



FM 3-34.331 



MM 

mn 

mo 

MOA 

Mon 

monument 



middle marker 



mean 



MOS 
movement area 



MRSE 

MSL 

MTP 

multipath errors 



multistation reduction 



month 

memorandum of agreement 

Monday 

any object or collection of objects that indicate the position on the 
ground of a survey station. In military surveys, the term 
monument usually refers to a stone or concrete station marker 
containing a special bronze plate on which the exact station point 
is marked 

military occupational specialty 

the runways (exclusive of apron areas), taxiways, and other areas 
of an airport/heliport, which are used for taxiing, takeoff, and 
landing of aircraft. At airports/heliports with a tower, specific 
approval for entry onto the movement area must be obtai ned from 
ATC 

mean radial spherical error 

mean sea level 

mission training plan 

errors caused when one or more reflected signals, interfering with 
the main signal because of their common time origin but different 
path lengths, are superimposed with their relative phase offsets 
on the primary signal at the receiver. Cyclic perturbations of the 
carrier are caused by this superimposition as the various signals 
undergo changes in their relative phase offsets as the geometric 
relation between the nearby and distant reflecting surfaces and 
the satellite and receiver changes 

geodetic parameters that are estimated at more than two stations 
using simultaneous observations 



n 

N 

NA 

NAD 

NAD 27 

NAD 83 

nadir 

NAS 

National Flight Data 
Center 



geoid height 

north 

not applicable 

North American Datum 

North American Datum of 1927 

North American Datum of 1983 

the point of the celestial sphere that is directly opposite the zenith 
and vertically downward from the observer 

National Airspace System 

a facility in Washington, District of Columbia, that was 
established by the FAA to operate a central aeronautical 
information service for the collection, validation, and 
dissemination of aeronautical data in support of the activities of 
the government, industry, and the aviation community. The 
information is published in the National Flight Data Digest 
(NFDD) 



Glossary-19 



FM 3-34.331 



National Flight Data 
Digest 



NATO 

NAVAI D 

NAVAI D survey 



NAVD 88 
navigable airspace 

navigational aid 

NAVSTAR 

NBC 

NCAD 

NCO 

NCOIC 

NDB 

NE 

NFDD 

NGRS 

NGS 

NGVD 29 

NIMA 

NL 

No. 

NOAA 

nondi recti onal beacon 



nonprecision approach 
procedure 

North American Datum 



a daily (except weekends and Federal holidays) publication of 
flight information (appropriate to aeronautical charts or 
aeronautical publications) that provides operational flight data 
which is essential to safe and efficient aircraft operations 

North Atlantic Treaty Organization 

navigational aid 

the process of determining the position and/or elevation of one or 
more NAVAI Ds and adjunctive points on associated runways or 
extended runway centerlines. A NAVAI D survey that is performed 
as part of theOC survey is called a combined NAVAI D survey. A 
NAVAI D survey that is not performed as part of a normal OC 
survey is called a special NAVAI D survey 

North American Vertical Datum of 1988 

airspace at and above the minimum flight altitude that is 
prescribed in FARs, including airspace needed for safe takeoff and 
landing 

any visual or electronic device, airborne or on the surface, which 
provides point-to-point guidance information or position data to 
aircraft in flight 

Navigation Satellite Timing and Ranging 

nuclear, biological, and chemical 

New Cumberland Army Depot 

noncommissioned officer 

noncommissioned officer in charge 

nondi rectional beacon 

northeast 

National Flight Data Digest 

National Geodetic Reference System 

National Geodetic Survey 

National Geodetic Vertical Datum of 1929 

National Imagery and Mapping Agency 

notes and legends 

number 

National Oceanic and Atmospheric Administration 

anL/MF orUHF radio beacon transmitting nondi recti onal signals 
whereby the pilot of an aircraft that is equipped with direction- 
finding equipment can determine his bearing to or from the 
station. When the NDB is installed in conjunction with an I LS 
marker, it is normally called a compass locator 

a standard instrument-approach procedure in which no electronic 
glide slope is provided (for example, VOR,TACAN, NDB, localizer, 
ASR, and simplified directional facility [SDF] approaches) 

the initial point of this datum is located at Meades Ranch, Kansas. 
Based on the Clarke spheroid of 1866, the geodetic positions of 
this system are derived from a readjustment of thetriangulation 
of the entire country in which Laplace azimuths were introduced 



20-Glossary 



FM 3-34.331 



Nov November 

NSATS number of satellites 

NSRS National Spatial Reference System 

NW northwest 



obs 
observer's meridian 

obstruction 



OC 

occ 

OCONUS 

Oct 

ODALS 

offset line 



OIS 

OM 

op 

open traverse 

OPORD 
order of accuracy 

ortho 
orthometric height 

OTF 
OVM 



observed 

a celestial meridian passing through the zenith (at the point of 
observation) and the celestial poles 

any object that penetrates a specified surface. An object that 
penetrates a supplemental surface is a supplemental obstruction. 
The most obstructing object in a set of objects is the one that 
penetrates an imaginary surface further than any other object in 
the set 

obstruction chart 

occupied 

outside continental United States 

October 

Omnidirectional Approach Light System 

a supplementary line that is close to and roughly parallel with a 
main line (measured offsets). When a line for which data are 
desired is in such a position that it is difficult to measure over it, 
the required data are obtained by running an offset line in a 
convenient location and measuring offsets from it to salient points 
on the other line 

obstruction identification surface 

outer marker 

operator 

a survey traverse which begins from a station of known or adopted 
position but does not end upon such a station 

operation order 

a mathematical ration that defines the general accuracy of 
measurements made in a survey (for example, first, second, third, 
fourth, or lower order) 

orthometric 

another name for the elevation of an object (the height of an object 
above the geoid) 

on the fly 

organization vehicle maintenance 



p page(s) 
PAC Personnel and Administration Center 
PACS primary airport control station 



Glossary-21 



FM 3-34.331 



PADS 

PAPI 

PAR 

parallax 



PBM 

PC 

P-code 

PDOP 

permanent benchmark 



PFC 
pgdn 

pgs 
pgup 

picture point 



PIR 

PLASI 

PLGR 

plumb line 

PM 

PMCS 

POC 

POL 

pos 

POV 

ppm 

PPS 

PRC 

precise ephemeris 



Position and Azimuth Determination System 

precision approach-path indicator 

precision approach radar 

the apparent displacement or the difference in apparent direction 
of an object as seen from two different points not on a straight line 
with the object; also, the angular difference in direction of a 
celestial body as measured from two points on the earth's orbit 

permanent benchmark 

personal computer 

precision code 

positional dilution of precision 

a BM of as nearly permanent character as it is practicable to 
establish. Usually designated simply as BM. A PBM is intended to 
maintain its elevation with reference to an adopted datum, 
without change, over a long period 

private first class 

page down 

pages 

page up 

a terrain feature that is easily identified on an aerial photograph 

and whose horizontal or vertical position or both have been 

determined by survey measurements. Picture points are marked 

on the aerial photographs by the surveyor and are used by the 

photomapper 

precise instrument runway 

pulse-light approach-slope indicator 

precise lightweight GPS receiver 

the line of force in a geopotential field; the continuous curve to 
which the direction of gravity is everywhere tangential; or, the 
line indicated by a plumb-bob cord 

post meridian 

preventive-maintenance checks and services 

point of contact 

petroleum, oils, and lubricants 

position 

privately owned vehicle 

part(s) per million 

Precise Positioning Service 

pseudorange correction 

the precise ephemeris isthepostprocessed position of a satellite in 
its orbit as a function of time. It is computed from data that are 
observed at tracking stations at fixed locations and is available 
from various global agencies 



22-Glossary 



FM 3-34.331 



precision approach 
procedure 



precision approach 
radar 



prime meridian 



prime vertical 



PRN 

pseudorange 
measurement 



PVC 
PX 



a standard instrument-approach procedure in which an electronic 
glide slope is provided or used (for example, I LS and PAR 
approaches) 

radar equipment usually located at military or joint-use airfields 
that detects and displays azimuth, elevation, and range of aircraft 
on the final approach course to a runway. The controller issues 
guidance to the pilot based on the aircraft's position and elevation 
relative to the touchdown point on the runway displayed on the 
radarscope 

the specific meridian (for example, line of longitude) that is 
assigned the value of zero and to which all other meridians are 
referenced. While Greenwich, E ngland, is almost universally 
accepted as the prime meridian, several other meridians (such as 
the meridian of Paris) remain in use 

the vertical circle through the east and west points of the horizon. 
It may be true, magnetic, compass, or grid depending upon which 
east or west points are involved 

pseudorandom noise 

a measurement obtained by comparing the time signal generated 
by the satellite clock to the time signal generated by the receiver 
clock to determine propagation time and, subsequently, the range 

polyvinyl chloride 

post exchange 



r 

Rl 

R2 

radar 



radar approach 




RC 




RDOP 




REIL 




rep 


right 


ascension 




RM 




RMS 



degrees of freedom 

reject value, use first mean value 

reject value, use second mean value 

a device for radio detection and ranging. Radar measures the time 
interval between transmitted and received radio pulses and 
provides information on the range, azimuth, and/or elevation of 
objects in the path of the transmitted pulse. A primary radar 
system uses reflected radio signals. A secondary radar system is a 
system wherein a radio signal that is transmitted from a radar 
station initiates the transmission of a radio signal from another 
station 

an instrument-approach procedure that uses PAR or ASR 

ratio of closure 

relative dilution of precision 

runway end identifier light 

repetition 

the angular distance that is measured eastward on the equator 
from the vernal equinox to the hour circle through the celestial 
body, from to 24 hours 

reference mark 

root-mean-square 



Glossary-23 



FM 3-34.331 



Ro rejected by observation 

RPP runway plans and profiles 

RT rel ocated th reshol d 

RTCM Radio Technical Commission for Maritime 

RTK real-time kinematic 

RTO radio/telephone operator 

runway a defined rectangular area on a land airport that is prepared for 
the landing and takeoff run of aircraft along its length 

RVR runway visual range 

RW runway visibility value 

rwy runway 



s 

S 

SI 

S3 

S4 

S/A 

SACS 

sampling interval (data 
rate) 

SATO 

SC 

SCP 

SDF 

SDNCO 

SE 

sees 

Sep 

SEP 

sexagesimal system 



SFC 

SGT 

SIC 

SIF 

simplified directional 
facility 



sin 
SINCGARS 



seconds 

south 

Adjutant (U nited States Army) 

Operations and Training Officer (United States Army) 

Supply Officer (U nited States Army) 

selective availability 

secondary airport control station 

the interval (in seconds) at which observations are logged to 
memory 

Scheduled AirlineTicket Office 

special committee 

survey control point 

simplified directional facility 

staff duty noncommissioned officer 

southeast 

seconds 

September 

spherical error probable 

a system of notation by increments of 60 (the division of a circle 
into 360°, each degree into 60 minutes, and each minute into 
60 seconds) 

sergeant first class 

sergeant 

survey information center 

stadia-interval factor 

a NAVAID that is used for nonprecision instrument approaches. 
The final approach course is similar to that of an I LS localizer, 
except that the SDF course may not be aligned with the runway 
and the course may be wider, resulting in less precision 

sine 

Single-Channel Ground-to-Air Radio System 



24-Glossary 



FM 3-34.331 



SLC 

SM 

software 



SOI 
solar day 



solar time 

SOP 

SPC 

SPCE 

SPCO 

spheroid 

SPHS 

spirit leveling 

SPS 

SSF 

SSG 

SSGCN 

SSI 

ST 

sta 

state-plane coordinate 
system 

std 
stopway 



STP 

sub 

SV 



sea-level coefficient 

soldier's manual 

GPS software is classified as data logging, postprocessing 
reduction, and real-time processing. Data-logging software relates 
to the operation of the receiver and is not field-tested. 
Postprocessing software should be tested using a BM data set 

signal operation instructions 

the interval of time from the transit of either the sun or the mean 
sun across a given meridian to the next successive transit of the 
same body across the same meridian; also, the duration of one 
rotation of the sun 

time based upon the rotation of the earth relative to the sun; time 
on the sun 

standing operating procedure 

specialist 

survey planning and coordination element 

survey planning and coordinating officer 

any figure differing slightly from a sphere 

specially prepared hard surface 

spirit leveling follows thegeoid and its associated level surfaces, 
which are irregular rather than any mathematically determined 
spheroid or ellipsoid and associated regular level surfaces 

Standard Positioning Service 

standard solution file 

staff sergeant 

Standards and Specifications for Geodetic Control Networks 

standing signal instructions 

special text 

station 

the meridian used as the axis of Y for computing projection tables 
for a state coord in ate system (theCM of the system usually passes 
close to the center of the figure of the area or zone for which the 
tables are computed) 

standard 

an area beyond the takeoff runway that is at least as wide as the 
runway, is centered upon the extended runway centerline, is able 
to support an airplane during an aborted takeoff without causing 
structural damage to the airplane, and is designated by airport 
authorities for use in decelerating the airplane during an aborted 
takeoff. The location of threshold lights has no bearing on an area 
being designated as a stop way 

soldier training publication 

subtract 

satellite vehicle 



Glossary-25 



FM 3-34.331 



t 

T 

TA 

TAB 

TACAN 

tactical air navigation 

tan 
target 

TBM 

TCMD 

TDY 

TDZE 

TEC 

TECHOPORD 

tel 

temp 

TG 

thr 

threshold 



tidal benchmark 



tidal datum 



TM 
TMP 
TOD 
TOE 
topo 
touchdown zone 



grid azimuth 

geodetic azimuths 

target acquisition 

target-acquisition battery 

tactical air navigation 

a UHF electronic rho-theta air NAVAID, which provides suitably 
equipped aircraft with a continuous indication of bearing and 
distance to theTACAN station 

tangent 

any object or point toward which something is directed; also, an 
object which reflects a sufficient amount of a radiated signal to 
produce an echo signal on detection equipment 

temporary benchmark 

transportation-control and movement document 

temporary duty 

touchdown zone elevation 

Topographic Engineering Center 

technical operation order 

telescope 

temperature 

trainer's guide 

threshold 

the beginning of that portion of the runway usable for landing. A 
DT is located at a point on the runway other than the designated 
beginning of the runway. The displaced area is available for 
takeoff or rollout of aircraft. The DT paint bar is entirely on the 
usable landing surface. A relocated threshold (RT) is located at a 
point on the runway other than the beginning of the full strength 
pavement. The area between the former threshold and the RT is 
not available for the landing or takeoff of aircraft. The abandoned 
runway area mayor may not be available for taxiing 

a BM set to reference a tide staff at a tidal station and the 
elevation that is determined with relation to the local tidal datum 

specific tide levels, which are used as surfaces of reference for 
depth measurements in the sea and as a base for the 
determination of elevation on land. Many different datums have 
been used, particularly for leveling operations 

technical manual 

transportation motor pool 

tabulated operational data 

table(s) of organization and equipment 

topographic 

the first 3,000 feet of the runway beginning at thethreshold 



26-Glossary 



FM 3-34.331 



touchdown zone 
elevation 



TP 

TRADOC 

transit 



transmi ssometer 



trig list 
tropospheric correction 



the highest elevation in the touchdown zone. The OC program 
specifications require that the TDZE will be determined only for 
runways with SPHSs equal to, or greater than, 3,000 feet in 
length 

temporary point 

United States Army Training and Doctrine Command 

the apparent passage of a star or another celestial body across a 
defined line of the celestial sphere, as a meridian, prime vertical, 
or almucantar; the apparent passage of a star or another celestial 
body across a line in the reticle of a telescope, or some line of sight; 
a theodolite with the telescope mounted so that it can be transited 

an apparatus used to determine visibility by measuring the 
transmission of light through the atmosphere and is the 
measurement source for determining runway visual range (RVR) 
and runway visibility value (RVV) 

an extremely or excessively precise list 

the troposphere causes a propagation delay of a GPS signal. This 
delay can be estimated using any recognized atmospheric model 
and can be mostly eliminated by relative positioning for short 
lengths and modeled for longer baselines 



UDS 

UERE 

UHF 

universal transverse 
Mercator 



UPS 

US 

USA 

USAADCENFB 

USAASA 

USACE 

USAES 

USAF 



user -defined sequence 

user equivalent range error 

ultrahigh frequency 

a series of 120 coordinate systems that are based on the 
transverse Mercator projection that was originally developed by 
the US Army for a worldwide mapping project. Sixty zones are 
used to map the northern hemisphere, and the remaining zones 
apply to the southern hemisphere. Each zone is 6° wide and is 
numbered. Zone 1 covers longitudes of 180° W through 174° W. 
The remaining zones are numbered sequentially as they move 
east. All zones have their origin at the equator, use the meter as 
the system unit, and have a false easting of 500,000 meters and a 
false northing of 0. A scale reduction factor of 0.9996 is used on all 
zones. Zones for the southern hemisphere are identical to their 
northern counterpart except that the false northing is set to 
10,000,000 to eliminate negative Y coordinates 

universal polar stereographic 

U nited States 

U nited States of America 

United States Army Air Defense Center and Fort Bliss 

U nited States Army Aeronautical Services Agency 

U nited States Army Corps of E ngi neers 

United States Army Engineer School 

United States Air Force 



Glossary-27 



FM 3-34.331 



USAPA United States Army Publishing Agency 

USAPPC United States Army Publications and Printing Command 

USCG United States Coast Guard 

USC&GS United States Coast and Geodetic Survey 

USGS U nited States Geological Survey 

UTC universal time, coordinated 

UTM universal transverse Mercator 



VASI 

VDOP 

vern 

vernal equinox 



vert 
vertical circle 



vertical control 



vertical -control datum 



very-high-frequency 
omnidirectional range 

very-high-frequency 

omnidirectional range 

and tactical air 

navigation 

VFR 

VHF 

VOR 

VORTAC 



visual-approach slope indicator 

vertical dilution of precision 

vernier 

that point of intersection of the ecliptic and the celestial equator, 
which is occupied by the sun as it changes from south to north 
declination on or about March 21 (same as the first of Aries, the 
first point of Aries, or the March equinox) 

vertical 

a great circleof the celestial sphere (through the zenith and nadir) 
that is perpendicular to the horizon; also, a graduated disk 
(mounted on an instrument in such a manner that the plane of its 
graduated surface can be placed in a vertical plane), which is used 
primarily for measuring vertical angles in astronomical and 
geodetic work 

the measurements taken by surveying methods for the 
determination of elevation only with respect to an imaginary level 
surface, usually the MSL 

any level surface (for example, the MSL) taken as a surface of 
reference from which to reckon elevations. Although a level 
surface is not a plane, the vertical-control datum is frequently 
referred to as the datum plane 

a VHF NAVAID, which provides suitably equipped aircraft with a 
continuous indication of bearing to the VOR station 

a navigational facility consisting of two components, a VOR and a 
TACAN, which provide VOR azimuth, TACAN azimuth, and 
TACAN distance 

visual flight rules 

very high frequency 

very-high-frequency omnidirectional range 

very-high-frequency omnidirectional range and tactical air 
navigation 



W west 
WAAS wide-area augmentation system 
WDI wind-direction instrument 



28-Glossary 



FM 3-34.331 



WGS 

WGS72 

WGS 84 

widelaning 



World Geodetic System 
1984 



World Geodetic System 
World Geodetic System 1972 
World Geodetic System 1984 

a linear combination of the measured phases of LI and L2, based 
on the frequency difference. Widelane ambiguities can be resolved 
easier than LI and L2 ambiguities, because the resulting 0.862- 
meter wavelength is much longer than the individual LI and L2 
wavelengths. Knowledge of the widelane ambiguity helps to solve 
the LI ambiguity, after which a simple computation will give the 
L2 ambiguity 

a global datum that is based on electronic technology, which is 
still to some degree classified. Data on the relationship of as many 
as 65 different datums to WGS-84 is available to the public. As a 
result, WGS 84 is becoming the base datum for the processing and 
conversion of data from one datum to any other datum. GPS is 
based on this datum. The difference between WGS 84 and NAD 83 
is small and is generally considered to be insignificant 



XVIII the Ta bl e 18 value extracted from DM S ST 045 

X, Y, and Z variables used to depict coordinates in theX, Y, and Z axis 

Y-code the military's classified, encrypted precision code 

yr year(s) 



ZD 

zen 

zenith 

zenith distance 



zenith distance 

zenith 

the point where an infinite extension of a plumb (vertical) line, at 
the observer's position, pierces the celestial sphere above the 
observer's head 

the complement of the altitude; the angular distance from the 
zenith of the celestial body measured along a vertical circle 



Glossary-29 



Bibliography 



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AR 210-20. Master Planning for Army I installations. 30 J uly 1993. 

AR 310-25. Dictionary of U nited States Army Terms. 15 October 1983. 

AR 310-50. Authorized Abbreviations and Brevity Codes. 15 November 1985. 

AR 380-5. Department of the Army I n formation Security Program. 
25 February 1988. 

AR 385-95. Army Aviation Accident Prevention. 10 December 1999. 

AR 405-10. Acquisition of Real Property and Interests Therein. 14 M ay 1970. 

AR 420-90. Fire and Emergency Services. 10 September 1997. 

AR 95-1. Flight Regulations. 1 September 1997. 

AR 95-2. Air Traffic Control, Airspace, Airfields, Flight Activities, and Navigation 
Aids. 10 August 1990. 

DA Form 1900. Conversion of Mean Time to Sidereal Time. 1 February 1957. 

DA Form 1901. Conversion of Sidereal TimetoMean Time. 1 February 1957. 

DA Form 1902. Conversion of Mean Timeto Apparent Time. 1 February 1957. 

DA Form 1903. Azimuth by Direction Method. 1 February 1957. 

DA Form 1905. Azimuth by Hour Angle Method. 1 February 1957. 

DA Form 1907. Azimuth by Altitude Method. 1 February 1957. 

DA Form 1909. Longitude by the Altitude of Stars N ear thePrimeVertical. 
1 October 1964. 

DA Form 1911. Altitude and Azimuth (Sin-Cos). 1 February 1957. 

DA Form 1914. Computation ofBaseLine. 1 February 1957. 

DA Form 1915. Abstract of Levels and Computation of Inclination Corrections. 
1 February 1957. 

DA Form 1916. Abstract of H or izonta I Directions. 1 February 1957. 

DA Form 1917. List of Directions. 1 February 1957. 

DA Form 1918. Computation of Triangles. 1 February 1957. 

DA Form 1920. TriangleComputation (for Calculating Machine). 
1 February 1957. 

DA Form 1921. Reduction to Center. 1 February 1957. 

DA Form 1922. Position Computation, Order Tri angulation 

(Logarithmic). 1 October 1964. 



Bibliography-1 



FM 3-34.331 



DA Form 1923. Position Computation, Order Tri angulation (for 

Calculating Machine Computation). 1 February 1957. 

DA Form 1924. Inverse Position Computation. 1 February 1957. 

DA Form 1925. Quadrilateral Adjustment (Least Squares Method). 
1 February 1957. 

DA Form 1927. Latitude and Longitude Adjustment. 1 February 1957. 

DA Form 1930. Special Angle Computation. 1 February 1957. 

DA Form 1931. Traverse Computation (Geographic). 1 February 1957. 

DA Form 1932. UTM Grid Coordinates From Geographic Coordi nates. 
1 February 1957. 

DA Form 1933. Geographic Coordi nates From UTM Grid Coordinates. 
1 February 1957. 

DA Form 1934. Grid Azimuths (t and T) and (t-T) Correction From UTM Grid 
Coordinates. 1 February 1957. 

DA Form 1935. Grid Azimuth (t) and Grid Length. 1 February 1957. 

DA Form 1936. List of Directions, UTM Grid. 1 February 1957. 

DA Form 1937. Computation of Triangles (UTM Grid). 1 February 1957. 

DA Form 1938. Position Computation (UTM Grid). 1 February 1957. 

DA Form 1939. Reduction of Taped Distances. 1 February 1957. 

DA Form 1940. Traverse Computation on theUniversal Transverse Mercator Grid. 
February 1957. 

DA Form 1941. Grid and Declination Computations. 1 February 1957. 

DA Form 1942. Computation of Levels. 1 February 1957. 

DA Form 1943. Abstract of Zenith Distances. 1 February 1957. 

DA Form 1944. Computation of Elevations and Refractions From Reciprocal 
Observations (Logarithmic). 1 February 1957. 

DA Form 1945. Computation of Elevations and Refractions From Reciprocal 
Observations (by Calculating Machine). 1 February 1957. 

DA Form 1947. Computation of Elevations From Nonreciprocal Observations (by 
Calculating Machine). 1 February 1957. 

DA Form 1948. Altimeter Leveling. 1 February 1957. 

DA Form 1949. Corrected Altimeter Readings Prorated According toTime. 
1 February 1957. 

DA Form 1953. Universal Polar Stereographic Transformations. 1 February 1957. 

DA Form 1954. P I aneCoordi nates From Geographic Coordi nates on the 

Transverse Mercator Projection (Calculating Machine Computation). 
1 February 1957. 



Bibliography-2 



FM 3-34.331 



DA Form 1955. Geographic Coordinates From Transverse Mercator Grid 
Coordinates (Calculating Machine Method). 1 February 1957. 

DA Form 1956. P I aneCoordi nates From Geographic Coordinates on the Lambert 
Projection (Calculating Machine Computation). 1 February 1957. 

DA Form 1957. Geographi c Coordinates F rom Lambert Gri d Coordinates 
(Calculating Machine Computation). 1 February 1957. 

DA Form 1958. Description or Recovery of Benchmark. 1 October 1964. 

DA Form 1959. Description or Recovery of H ori zontal Control Station. 
1 October 1964. 

DA Form 1962. Tabulation of Geodetic Data. 1 February 1957. 

DA Form 201. Military Personnel Records} acket, US Army. 1 August 1971. 

DA Form 2028. Recommended Changes to Publications and Blank Forms. 
1 February 1974. 

DA Form 2404. Equipment Inspection and Maintenance Worksheet. 1 April 1979. 

DA Form 2839. Latitude From Zenith Distance of Polaris. 1 October 1964. 

DA Form 2847. Comparison of Chronometer and Radio Signals. 1 October 1964. 

DA Form 2850. Astronomic Results. 1 October 1964. 

DA Form 2854. Electronic Distance Measurement Summary. 1 October 1964. 

DA Form 2855. Geodi meter (Model 4) Observations and Computations. 
1 October 1964. 

DA Form 2856. Field Sheet, Tel I urometer Data Entries (MR A3 MK11). 
1 October 1964. 

DA Form 2857. Field Sheet, Micro-Chain Data Entries. 1 October 1964. 

DA Form 348. E qui pment Operator's Qualification Record. 1 October 1964. 

DA Form 4253. Horizontal Direction or AngleBook. J une 1974. 

DA Form 4446. Level, Transit, and General Survey Record. November 1975. 

DA Form 4648. Station Description Book. September 1977. 

DA Form 4856. Developmental Counseling Form. J une 1999. 

DA Form 5817-R. Zenith Di stance/ Vertical Angle (LR A). August 1989. 

DA Form 5818-R. General Survey Notes (LRA). August 1989. 

DA Form 5819-R. Field Sheet, Infrared (LRA). August 1989. 

DA Form 5820-R. Three-Wire Leveling (LRA). August 1989. 

DA Form 5821-R. Airfield Compilation Report (LRA). August 1989. 

DA Form 5822-R. Precision Approach Radar (GCA) Data (LRA). August 1989. 

DA Form 5827-R. Instrument Landing System Data (LRA). August 1989. 



Bibliography-3 



FM 3-34.331 



DA Pamphlet 25-30. Consolidated Index of Army Publications and Blank Forms. 
1 July 2000. 

DA Pamphlet 310-35. 1 ndex of I nternational Standardization Agreements. 
15 December 1978. 

DD Form 1351-2. Travel Voucher or Subvoucher. August 1997. 

DD Form 1610. Request and Authorization for TDY Travel ofDOD Personnel. 
1 June 1967. 



NOTE : These publications are available from DMS, Fort Bel voir, Virginia 
22060-5828. 

DMS Form 16-7. Horizontal Directions/ Zenith Distances. 1 November 1975. 

DMS Form 5820-R. Collimation Check. J anuary 1997. 

DMS ST 005. Geometric Geodetic Accuracy Standards and Specifications for 
Using GPS Relative Positioning Techniques. J uly 1997. 

DM S ST 031. Standards and Specifications for Geodetic Control Networks. 
J uly 1997. 

DM S ST 032. Specifications to Support Classification, Standards of Accuracy, and 
Specifications of Geodetic Control Surveys. October 1997. 

DMS ST 045. UTM Grid Tables- Clark 1866, Volumes I and II. April 2000. 

DMS ST 096. Real-TimeKinematic with TrimMap™ SoftwareTraining Manual. 
J anuary 1997. 

DMS ST 097. GPSurvey™ Software2.2T raining Manual. J anuary 1997. 

DMS ST 648. Al SI (Automated I ntegrated Survey I nstrument) Operations. 
March 1998. 



NOTE : These publications are available from the USACE Publication 
Depot, Attention: CE I M-l M-PD, 2803 52nd Avenue, Hyattsville, Maryland 
20781-1102. 

EM 1110-1-1002. Survey Markers and Monu mentations. 14 September 1990. 

EM 1110-1-1003. NAVSTAR Global Positioning System Surveying. 1 August 1996. 

EM 1110-1-1005. Topographic Surveying. 31 August 1994. 



NOTE : These publications are available from the US Department of 
Transportation, FAA, 800 Independence Avenue, Southwest, Washington, 
District of Columbia 20591. 

FAA 405. Standardsfor Aeronautical Surveysand Related Products, Fourth 
Edition. September 1996. 

FAA-7350.5-V. FAA Location Identifiers. February 1989. 



Bibliography-4 



FM 3-34.331 



FAR-77. Objects Affecting Navigable Airspace. 15 J uly 1996. 

FM 101-5. Staff Organization and Operations. 31 May 1997. 

F M 101-5-1. Operational Terms and Graphics. 30 September 1997. 

FM 21-26. Map Reading and Land Navigation. 7 May 1993. 

FM 21-31. Topographic Symbols. 19 J unel961. 

F M 24-1. Signal Support in the Airland Battle 15 October 1990. 

FM 5-105. Topographic Operations. To be published within six months. 

FM 5-233. Construction Surveying. 4 J anuary 1985. 

FM 5-553. General Drafting. 6 J anuary 1984. 

FM 55-10. Movement Control. 9 February 1999. 

FM 6-2. Tactics, Techniques, and Procedures for Field Artillery Survey. 
23 September 1993. 

Glossary of M appi ng, Charting, and GeodeticTerms (Fourth Edition, 1981). Pre- 
pared by DMA, Hydrographic/Topographic Center, 6500 Brookes Lane, 
Washington, District of Columbia 20315. 1981. 

NFDD. Prepared by NIMA, Hydrographic/Topographic Center, 6500 Brookes 
Lane, Washington, DC 20315. 

STP 5-82D14-SM-TG. Soldier's Manual and Trainer's Guide: 82D, Topographic 
Surveyor (Skill Level 1/2/3/4). 3 May 1985. 

TM 5-232. Elements of Surveying. 1J unel971. 

TM 5-235. Special Surveys. 18 September 1964. 

TM 5-237. Surveying Computer's Manual. 30 October 1964. 

TM 5-6675-230-15. Operator's, Organizational, Field and Depot Maintenance 

Manual: Level, Surveying: PreciseTilting; 3-Level Screws, Electriclllumi- 
nation, 10-Inch Telescope (Military Model 10-X) with Tripod. 6 J une 1962. 

TM 5-6675-239-15. Organizational, Direct Support, General Support, and Depot 
Maintenance Manual Including Repair Parts for L ight, Signal, Surveying; 
5-Inch Diameter Reflector; GrilleHousing; in Carrying Case (Military 
Design). 15 J une 1965. 

TM 5-6675-244-15. Organizational, Direct Support, General Support, and Depot 
Maintenance Manual (Including Repair Parts and Special ToolsList); 
Target Set, Surveying, Circular Level and Optical Plummet in Tribrach 
with Quick Release Mechanism (Wild Heerbrugg Model T-2). 
12 April 1966. 

TM 5-6675-298-15. Operator, Organizational, Direct Support, General Support, 

and Depot Maintenance Manual: Theodolite, Surveying: Directional, 0.002 
Mil Graduation with Extension L eg Tripod (Keuffd and Esser Model KE-2 
Special). 16 September 1968. 



Bibliography-5 



FM 3-34.331 



TM 5-6675-306-14. Operator's, Organizational, Direct Support, and General 
Support Maintenance Manual: Theodolite, Directional; 1-Second 
Graduation, 5.9-1 nch-Long Telescope, DetachableTribrach with 
Accessories and Tripod (Wild Heerbrugg Model T2-74 Deg)., 9-Inch Long 
Telescope, DetachableTribrach with Accessories and Tripod (Wild 
Heerbrugg Model T2-74 Deg). 23 J uly 1975. 

TM 5-6675-318-114-1/2. Operator's, Organizational, Direct Support, and General 
Support Maintenance Manual for Topographic Support System, Survey 
Section, Model ADC-TSS-6. 3 September 1985. 

TM 5-6675-329-13&P-HR. Hand Receipt Manual Covering Contents of 

Components of End Item (COEIs), Basic Issue I terns (Bll), and Additional 
Authorizations L ist (AAL) for Sdf-L eveling Surveying L eve! (Wild 
H eerbrugg M ode! NA 2-80). 9 November 1983. 

TM 5-6675-332-10. Operator's Manual for Automated I ntegrated Survey 

Instrument (Al SI) Typel Topographic, Part Number 571146150, Typell 
Construction, Part Number 571146152 Operators Manual, Automated 
I ntegrated Survey I nstrument (AISI), Typel, Topographic. 30 J unel994. 

TM 5-803-7. Civil Engineering Programming: Airfield and Heliport Planning and 
Design Criteria. 1 April 1999. 

TOE 05540LA00. Topographic Planning and Control Team. J une 1998. 

TOE 05606L000. Headquarters, and Headquarters Company, Engineer Battalion 
(Topographic) Theater Army. J une 1998. 

TOE 05607L0. Engineer Company (Topographic) (EAC), Engineer Battalion 
(Topographic). 1998. 

TOE 05608L0000. Engineer Company (Topographic) (Corps). J une 1998. 



Bibliography-6 



Index 



Numerics 

1 D, see one dimensional (1 D) 
2D, see two dimensional (2D) 
3D, see three dimensional (3D) 



absolute positioning 1-4, 8-1, 8-2, 

8-5,8-14 
abstract 5-8, 5-1 
accuracy 1 -3, 1 -5, 8-1 8, 8-20, 8-24, 

8-27,8-31,8-36,8-38,8-41, 

8-43, 8-45-47, 8-54-56, 8-61 , 

8-62,8-67,8-68,9-1,9-3, 

10-7, B-10, B-12, B-14, B-16, 

B-17 

external 8-56, 8-57 

internal 8-56, 8-57 

relative 8-20, 8-60, 8-66 
ADA, see air-defense artillery 

(ADA) 
adjustment 6-8 

Adjutant General (AG) 2-5, 2-6 
administrative-recon trip 2-9 
AE, see allowable error (AE) 
AEC, see angular error of closure 

(AEC) 
aerial photographs 3-5 
AG, see Adjutant General (AG) 
air-defense artillery (ADA) 1-1,1 -3, 

1-9,9-1,9-2,9-4 
airfield surveys 1-2 
airport imaginary surface 10-5 
airport location point (ALP) 10-10 
airport obstruction chart (AOC) 1 -2, 

10-1, 10-2, 10-9. See also 

survey, AOC 
airport reference point (ARP) 10-3, 

10-7, 10-9, 10-10 
airport surveillance radar (ASR) 

10-2 
AISI, see automated integrated 

survey instrument (AISI) 
allowable error (AE) 1-15, 6-5, 6-7, 

7-9, C-12, C-20, C-29 
ALP, see airport location point 

(ALP) 
ambiguity 8-39 



American Society of 

Photogrammetry and Remote 

Sensing (ASPRS) 8-20 
American Standard Code for 

Information Interchange 

(ASCII) 5-31 
angle 1-12, 5-1,5-2, 5-8, 6-2, 6-4, 

6-5 

deflection 5-1 

interior 5-1 

vertical 5-1 , 8-25 
angular error of closure (AEC) 6-4, 

6-5, C-11, C-12 
antispoofing (AS) 8-2, 8-6, 8-8, 

8-19,8-45 
AO, see area of operation (AO) 
AOC, see airport obstruction chart 

(AOC) 
approach/departu re-clearance 

surface 10-5 
area files 5-28 
area of operation (AO) 1-3, 2-7, 

9-2, 9-3 
Army 1 -5 
Army Training and Evaluation 

Program (ARTEP) 2-2 
ARP, see airport reference point 

(ARP) 
ARTEP, see Army Training and 

Evaluation Program (ARTEP) 
artillery surveys 1-6 
AS, see antispoofing (AS) 
ASCII, see American Standard 

Code for Information 

Interchange (ASCII) 
ASPRS, see American Society of 

Photogrammetry and Remote 

Sensing (ASPRS) 
ASR, see airport surveillance radar 

(ASR) 
atmospheric conditions 2-7 
automated integrated survey 

instrument (AISI) 1 -4, 1 -8, 5-6, 

5-10,5-13,5-15,5-24,5-25, 

5-28-30, 6-1 

batteries 5-30 

maintenance 5-29 

transporting 5-29 



azimuth 8-25, 8-27, 8-29 
azimuth mark 3-1 1,3-15, 6-1 



B 

baseline B-8 

basic-control surveys 1-6 
batteries 2-7 

benchmark (BM) 1-6, 1-13,3-4, 
3-6,7-2,7-5,7-6,8-17,8-66, 
11-31, C-28, C-29 
BM, see benchmark (BM) 
briefing 11-1, 11-8 
deliberate 11-8 
decision 11-9 
information 11-8 
mission 11-9 
staff 11-10 
impromptu 11-8 
procedure 11-11 
project 11-15 
broadcast-ephemeris information 
8-32 



C/A-code, see coarse-acquisition 

code (C/A-code) 
C&R, see curvature and refraction 

(C&R) 
CAD, see computer-aided design 

(CAD) 
CADD, see computer-aided design 

and drafting (CADD) 
carrier signals 8-1 9. See also 

L-band 
Cartesian coordinates 8-68 
C-check, see collimation test for 

leveling (C-check) 
central meridian (CM) 4-3, 5-14 
CEP, see circular error probable 

(CEP) 
C-factor, see collimation error 

(C-factor) 
circular error probable (CEP) 8-12, 

8-14 
clear-zone surface 10-5 
closed loop 5-1 



lndex-1 



FM 3-34.2 



CM, see central meridian (CM) 
coarse-acquisition code 

(C/A-code) 8-3-5, 8-19, 8-37, 

8-46-48, B-12, B-13 
code phase 8-30 
collimation error (C-factor) 7-2, 7-5, 

7-8, 7-9, C-24 
collimation test for leveling 

(C-check) 7-2, 7-4, 7-5, 7-9 
communication 1-17, 3-16, 5-29, 

8-38 
computer-aided design (CAD) 1-9, 

1-10,5-24,5-30 
computer-aided design and 

drafting (CADD) 1-9 
conical surface 10-4 
construction surveyors 1-3 
construction surveys 1-6. See also 

survey 
continental US (CONUS) 1 -7, 8-21 , 

8-27, 10-7 
control network 2-3 
control segment 8-3 
control survey 5-1 . See also survey 
CONUS, see continental US 

(CONUS) 
coordinate systems 4-6 

geographic coordinates 4-7 

high-accuracy reference 
networks 4-9 

NAD 27 4-8 

NAD 83 4-8 

National Geodetic Reference 
System 4-9 

US Military Grid-Reference 
System 4-6 

UTM grids 4-6 

WGS-84 ellipsoid 4-8 

World GEOREF System 4-7 
Corps Conversion (Corpscon) 

4-10,8-21 
Corpscon, see Corps Conversion 

(Corpscon) 
curvature and refraction (C&R) 

C-27 
customer 2-1 
cycle slips 8-18, 8-50 



data recording unit (DRU) 5-24, 

5-28 
datum 4-1 , 7-1 , 8-21 , 8-57, 8-68, 

10-10, B-10, B-14 



DE, see difference in elevation 

(DE) 
Defense Mapping School (DMS) 

1-5 
Department of Defense (DOD) 1 -5, 

8-1 , 8-2, 8-4-6 
DGPS, see Differential GPS. See 

also Global Positioning 

System (GPS) 
difference in elevation (DE) 1-13, 

5-13,7-4,7-5, C-28, C-29 
difference in the horizontal aim 

5-25 
difference in the vertical aim 5-25 
Differential Global Positioning 

System (DGPS), see 

Differential GPS (DGPS) 
Differential GPS (DGPS) 1-4, 1-9, 

4-8,8-2,8-18,8-19,8-35,8- 

66, B-6, B-13. See also 

Global Positioning System 

(GPS) 
differential leveling 3-2, 7-1, 7-4-6 

field party 7-6 

recording 7-6 

steps 7-5 
differential positioning 1-4, 8-2, 

8-14, 8-15. See also relative 

positioning 
dilution of precision (DOP) 8-6, 8-9, 

8-10, B-11 
distance measuring equipment 

(DME)1-4 
DIVARTY, see division artillery 

(DIVARTY) 
division artillery (DIVARTY) 9-1, 

9-2, 9-4 
DME, see distance measuring 

equipment (DME) 
DMS, see Defense Mapping 

School (DMS) 
DOD, see Department of Defense 

(DOD) 
DOP, see dilution of precision 

(DOP) 
Doppler 8-48 
DRU, see data recording unit 

(DRU) 
dynamic 8-1 
dynamic surveying 1-9 



EAC, see echelons above corps 
(EAC) 



earth centered earth fixed (ECEF) 

4-8, 8-21 
earth's curvature 5-14 
ECEF, see earth centered earth 

fixed (ECEF) 
echelons above corps (EAC) 9-1 , 

9-2, 9-4 
EDM, see electronic distance 

measurement (EDM) 
EDM traverse 8-60. See also 

electronic distance 

measurement (EDM) 
EDME, see electronic DME. See 

also electronic distance 

measurement (EDM) and 

distance measuring 

equipment (DME) 
electronic distance measurement 

(EDM) 1-16, 1-17,5-13,8-1, 

8-42, 8-58, 8-59, 8-62 
electronic distance measuring 

equipment (EDME) 1-8, 1-9, 

3-2, 5-13,5-15,6-1,6-3,8-27, 

11-32, 11-33. See also 

electronic distance 

measurement (EDM) and 

distance measuring 

equipment (DME) 
electronic DME (EDME), see 

electronic distance measuring 

equipment (EDME) 
ellipsoid 4-1 , 4-2, 8-1 3, 8-53, 8-65, 

C-4 
ellipsoidal height 8-17, 8-18, B-9, 

B-17 
ephemerides 8-4, 8-5 
ephemeris 8-7, 8-37, 8-47, 8-50 

data 8-32 

errors 8-47 
error sources 8-18 
existing control 8-24, 8-27 
existing control stations 3-4 
existing data 3-3. See also recon, 

office 



FA, see field artillery (FA) 
FA surveyors 1-6 
FAA 405 10-2, 10-7-10 
FAA, see Federal Aviation 

Administration (FAA) 
FAO, seefinance accounting office 

(FAO) 
FAR-77 10-2, 10-5, 10-8, 10-9 



lndex-2 



FM 3-34.2 



Federal Aviation Administration 

(FAA) 1-7, 10-1, 10-10 
Federal Geodetic Control 

Committee (FGCC) 2-3, 7-2, 

7-5, 7-6 
Federal Geodetic Control 

Subcommittee (FGCS) 8-24, 

8-27, 8-28, 8-56, 8-66, 8-67, 

9-1 
FGCC, see Federal Geodetic 

Control Committee (FGCC) 
FGCS, see Federal Geodetic 

Control Subcommittee 

(FGCS) 
field artillery (FA) 1-1, 1-3, 1-9, 

1-13,3-3,9-1,9-2,9-4 
field notes 1-14, 1-17 

abbreviations 1-15 

checks 1-17 

corrections 1-15 

description 1-15 

records 1-17 

sketches 1-14 

symbols 1-15 

tabulations 1-14 
field survey 1 -3 
finance accounting office (FAO) 

2-5,2-6, 11-20 
fire support (FS) 9-3 
fire-support coordinator 

(FSCOORD) 9-3 
first-order geodetic triangulation 

1-7 
fixed control 8-29 
FO, see forward observers (FO) 
forward observer (FO) 9-2 
fragmentary order (FRAGO) 11-13, 

11-15, 11-27 
FRAGO, see fragmentary order 

(FRAGO) 
FS, see fire support (FS) 
FSCOORD, see fire-support 

coordinator (FSCOORD) 



G2 9-3 

G3 9-2, 9-3 

GCA, see ground-controlled 

approach (GCA) 
GDOP, see geometric DOP 
general support (GS) 1-1, 2-6, 9-1 
geodetic surveys 1-4 
geographic coordinates 4-7 



geographic information system 

(GIS) 8-37 
geoid 1-3,4-1,8-17,8-53,8-66, 

B-9, B-16, B-17 
geoid height 8-18, B-16 
geoidal separation 8-21 
geometric DOP (GDOP) 8-10, 
8-1 9, B-1 1 . See also dilution of 
precision (DOP) 
GIS, see geographic information 

system (GIS) 
Global Positioning System (GPS) 
1-1, 1-4, 1-6, 1-7, 1-10-12, 
1-16, 1-18,3-1,3-4, 3-5,4-8, 
8-1,8-3-10,8-13,8-14, 
8-16-18,8-20,8-24,8-28, 
8-39,8-42,8-46,8-51,8-53, 
8-55,8-62,8-65,8-66, 10-7, 
11-21, 11-28, B-5, B-6, B-10, 
B-11, B-13, B-17 
accuracy 8-10 
adjustment 8-54, 8-55, 

8-58-60, 8-65, 8-66 

constrained 8-61, 8-66, 
8-68 

external 8-59 

internal 8-58 
antenna-swap calibration 8-43 
baseline 8-24 
control 8-28 
data 8-1 7, 8-36, 8-38, 8-40, 

8-44,8-61, 11-21, B-1 5 

archival 8-54 

processing 8-44, 8-45, 
8-49 

reduction 8-41 
data processing 8-45 
DGPS correction 8-38 
double differencing 8-48, 

8-49, 8-50 
epoch 8-48, 8-50, 8-51 
equipment requirements 8-31 
error measurement 8-54 
errors 8-10, 8-19 
lock, loss of 8-44 
network 1 -9, 8-21 , 8-28, 8-31 
network design B-6 
observation 8-28 
observation window 8-40 
occupation time 8-40 
planning 8-21 
point positioning 8-36 
positioning 8-5 
postprocessing 8-51 8-53 
procedures 8-35 



processing 8-48 

range accuracy 8-9 

raw data 8-54 

receiver 1-5, 8-1, 8-2, 8-7 

redundancy B-8 

repeatability 8-51 

satellite 8-2, 8-3, 8-7, 8-27 

satellite lock 8-42 

sessions 3-1 

signal 8-2, 8-7, 8-8, 8-25, 8-47 

single differencing 8-48 

site constraints 8-43. See also 
GPS, site selection 

site selection 8-43 

software 8-35 

survey 1-9 

surveying 1-18, 3-1, 3-6 

traversing 8-28 

triple differencing 8-49, 8-50 
GPS, see Global Positioning 

System (GPS) 
GPS-S, see GPS-Survey (GPS-S). 

See also Global Positioning 

System (GPS) 
GPS-Survey (GPS-S) 1-4, 5-30, 

8-1 1 , 8-20, 8-22, 8-23, 8-27, 

8-31,8-32,8-35,8-44,8-47, 

8-55-61,8-63, 8-68, 9-2, B-6, 

B-9, B-10, B-1 4. See also 

Global Positioning System 

(GPS) 
gravity 5-14 
grid system 4-6 
grids 4-3 
ground-controlled approach (GCA) 

10-10 
GRS 80 8-21 
GS, see general support (GS) 



H 

HARNs, see high-accuracy 

reference networks (HARNs) 
HDOP, see horizontal DOP 

(HDOP) 
heliport 10-5 

approach surface 10-5 

primary surface 10-5 
heliport transitional surface 10-5 
high-accuracy reference networks 

(HARNs) 4-9, 8-24 
horizontal control 8-66 
horizontal DOP (HDOP). See also 

dilution of precision (DOP) 

8-11,8-19 



lndex-3 



FM 3-34.2 



hydrographic surveys 1-6, 1-7 



I 

IEW, see intelligence and 

electronic warfare (IEW) 
ILS, see instrument landing system 

(ILS) 
Inertial Navigation System (INS) 

1-2 
inertial surveys 1-7 
initial site-visitation trip (ISVT) 2-8, 

2-9, 11-13, 11-14, 11-22 
inner horizontal surface 10-3, 10-5 
INS, see Inertial Navigation 

System (INS) 
inspection surveys 1-7 
instrument landing system (ILS) 

10-2,10-10 
intelligence and electronic warfare 

(IEW) 9-3 
ISVT, see initial site-visitation trip 

(ISVT) 



JAG, see Judge Advocate General 

(JAG) 
job files 5-28 
joint-level commands 1-5 
Judge Advocate General (JAG) 

3-7, 11-4 



K 

kinematic 8-1 , 8-2, 8-15-1 7, 8-21 , 
8-24, 8-26-28, 8-39, 8-43, 
8-44, B-5, B-11, B-13. See 
also dynamic 

kinematic, stop-and-go 8-1 5, 8-1 6, 
8-39,8-42,8-45, B-5, B-12, 
B-13 



L1 signal 8-3, 8-4, 8-8, 8-15, 8-19, 
8-44,8-46, B-12, B-15 

L2 signal 8-3, 8-4, 8-8, 8-15, 8-19, 
8-45, B-12, B-15 

land surveys 1-7 

landowner permission 3-7 

L-band 8-3 

LEC, see linear error of closure 
(LEC) 



level line 3-4, 11-21, 11-28 
leveling 7-1 , 8-68, 1 1 -32, B-1 , B-9, 

B-16, B-17 

automatic 7-1 

differential 8-68, B-1 

digital 7-1 

optical-micrometer 7-2 

precision 7-2 

rod 7-2 

trigonometric 8-68 
line of position (LOP) 3-6 
linear error of closure (LEC) 6-7, 

C-20 
logistics 2-6 
loop 

closure 8-51 , 8-53. See also 
traverse closure 

misclosure 8-60, 8-68 

misclosure ratio 8-53 
LOP, see line of position (LOP) 



M 

MACOM, see Major Army 

Command (MACOM) 
Major Army Command (MACOM) 

2-5,2-6, 11-14 
map 3-3, 3-5, 4-3, 5-1 , 8-25, 9-2, 

10-10, 11-5 

geographic-mapping point 
8-36 

projection 4-1 , 4-3 

topographic 8-17, 8-32, 1 1-31 

US military 4-3, 4-7 
mean sea level (MSL) 1 -3, 4-1 , 4-9, 

7-1,8-17,8-18, B-6, B-9 
megahertz 8-3 
meridians 4-3 

MGRS, see US Military Grid- 
Reference System (MGRS) 
microwave landing system (MLS) 

10-2 
Military Grid-Reference System 

(MGRS) 4-6 
minimally constrained adjustment 

B-16, B-17 
MLRS, see multiple-launch rocket- 
system (MLRS) 
MLS, see microwave landing 

system (MLS) 
monument 3-5 

commercial 3-11 

guard post 3-12 

nonstandard 3-12 

precast 3-9 



reference mark (RM) 3-1 1 

standard 3-8 

subsurface station marks 3-8 

surface station marks 3-8 

type A 3-9 

type C 3-9 

type G 3-9 

witness post 3-12 
MSL, see mean sea level (MSL) 
multipath 8-8 
multiple-launch rocket system 

(MLRS) 1-1, 9-1,9-2,9-6 



N 

NAD 27 1-7, 4-8-10, 8-14, 8-21, 

8-24, 8-57 
NAD 83 1-7, 4-8-10, 8-14, 8-21, 

8-24,8-55,8-59,8-61, 10-7 
nadir 5-1 
NAS, see National Airspace 

System (NAS) 
National Airspace System (NAS) 

1-2 
National Geodetic Reference 

System (NGRS) 4-9, 8-22, 

8-23, 8-25, 8-27, 8-29, 8-55, 

8-56, 8-58, 8-59, 8-61 
National Geodetic Survey (NGS) 

3-3,4-9,8-5,8-61,8-66,8-67, 

11-14, B-6 
National Imagery and Mapping 

Agency (NIMA) 1-1-3, 1-9, 

3-8,4-1,4-10,8-37,9-2,11-14 
National Ocean Service (NOS) 

8-24 
National Oceanic and Atmospheric 

Administration (NOAA) 11-14 
National Spatial Reference System 

(NSRS) 1-2, 10-1 
NAVAID, see navigational aid 

(NAVAID) 
NAVD88 4-9, 10-7 
Navigation Satellite Timing and 

Ranging (NAVSTAR) 1-1,1 -6, 

1-8,8-1-4,8-14 
Navigation Satellite Timing and 

Ranging Global Positioning 

System (NAVSTAR GPS) 1 -1 , 

1-4, 1-8,8-1,8-2,8-4,8-14 
navigational aid (NAVAID) 1-2, 

10-1,10-2,10-9,11-22,11-26, 

11-28 

surveys 1-6 



lndex-4 



FM 3-34.2 



NAVSTAR, see Navigation 

Satellite Timing and Ranging 

(NAVSTAR) 
NAVSTAR GPS, see Navigation 

Satellite Timing and Ranging 

Global Positioning System 

(NAVSTAR GPS) 
NCOIC, see noncommissioned 

officer in charge (NCOIC) 
NDB, see nondirectional beacon 

(NDB) 
network 1 -7 

auxiliary vertical-control 1 -8 

basic horizontal-control 1-7 

basic vertical-control 1 -8 

horizontal auxiliary-control 
1-8 

supplementary horizontal- 
control 1-8 

supplementary vertical-control 
1-8 
networks 3-4 
new station 3-5 
NGRS, see National Geodetic 

Reference System (NGRS) 
NGS, see National Geodetic 

Survey (NGS) 
NGS control 8-24 
NGVD29 1-7,4-9 
NIMA, see National Imagery and 

Mapping Agency (NIMA) 
NOAA, see National Oceanic and 

Atmospheric Administration 

(NOAA) 
noncommissioned officer in charge 

(NCOIC) 2-1 
nondirectional beacon (NDB) 10-2 
NOS, see National Ocean Service 

(NOS) 
NSRS, see National Spatial 

Reference System (NSRS) 



observation precautions 5-3 

instrument adjustment 5-3 

instrument check 5-3 

signal and target centering 5-3 
obstruction chart (OC) 1 0-9 
obstruction identification surface 

(OIS) 10-2 
OC, see obstruction chart (OC) 
OCONUS, see outside CONUS 

(OCONUS) 
office work 1-15 



adjusting 1-16 

computing 1-15 
OIS, see obstruction identification 

surface (OIS) 
one dimensional (1 D) 8-1 1 
on the fly/real-time kinematic (OTFV 

RTK)8-15, 8-16, 8-39, 8-45, 

B-5, B-13 
operation order (OPORD) 11-1, 

11-15, 11-26, 11-30 
Operations and Training Officer 

1-3 
OPORD, see operation order 

(OPORD) 
orthometric height 8-1 7, 8-1 8, B-1 , 

B-6, B-1 7 
OTF/RTK, see on the fly/real-time 

kinematic (OTF/RTK) 
outer horizontal surface 10-4, 10-5 
outside CONUS (OCONUS) 8-21, 

8-59 



PAC, see Personnel and 

Administration Center (PAC) 
PADS, see Position and Azimuth 

Determination System 

(PADS) 
PAR, see precision approach radar 

(PAR) 
parallels 4-3 

PBM, see permanent BM (PBM) 
PC, see personal computer (PC) 
P-code, see precision code 

(P-code) 
PDOP, see positional DOP 

(PDOP) 
permanent BM (PBM) 1-8. See 

also benchmark (BM) 
permanent monument 3-5 
personal computer (PC) 1-8-10, 

1-15,5-28,5-30,7-1,8-31, 

8-40,8-41, 8-43,8-46,8-61, 

8-63 
Personnel and Administration 

Center (PAC) 2-5, 2-6 
PIR, see precise-instrument 

runway (PIR) 
plane survey 1-4, 1-6 
plotter 5-31 

POC, see point of contact (POC) 
point of contact (POC) 1 1 -4, 1 1 -7, 

11-23, 11-26 



Position and Azimuth 

Determination System 

(PADS) 1-7, 1-12,3-2,9-4 
positional DOP (PDOP) 8-1 0, 8-19, 

8-32, B-1 1, B-13. See also 

dilution of precision (DOP) 
postprocessing 8-46 
PPS, see Precise Positioning 

Service (PPS) 
PRC, see pseudorange correction 

(PRC) 
Precise Positioning Service (PPS) 

1-4, 1-8,8-2,8-4,8-5,8-36 
precise instrument runway (PIR) 

10-10 
precision approach radar (PAR) 

10-2, 10-10 
precision code (P-code) 8-2-5, 

8-8,8-9,8-19,8-37,8-47, 

8-48, B-1 2 
primary surface 10-4, 10-5 
PRN, see pseudorandom noise 

(PRN) 
project completion 2-6 
project control 8-23 
project execution 2-9 
project planning 2-1 , 2-9 

accuracy 2-3 

administrative support 2-5 

communication 2-6 

deploys 2-5 

evaluation 2-1 

initial site-visitation trip 2-8 

logistics 2-6 

milestones 2-3 

movement plans 2-6 

project schedules 2-4 

project-visitation trip 2-9 

requirements 2-1 

scheduling 2-1 

timeline 2-3 
project specifications 8-27 
projection 4-1 , 4-3 

map 4-1 

Mercator 4-3 
project-visitation trip 2-9 
pseudokinematic 8-15, 8-16, 8-28, 

8-39,8-44, B-5, B-13 
pseudorandom noise (PRN) 1-5, 

8-1,8-3,8-39 
pseudorange 8-4-6, 8-14, 8-18, 

8-19,8-47, B-5 
pseudorange correction (PRC) 

8-14,8-37,8-38 



lndex-5 



FM 3-34.2 



Radio Technical Commission for 

Maritime (RTCM) 8-37, 8-38 
rapid static 8-15, 8-16, 8-39, 8-45, 

B-5, B-10, B-12, B-13. See 

also survey 
ratio of closure (RC) 6-7, C-20 
RC, see ratio of closure (RC) 
RDOP, see relative DOP (RDOP). 

See also dilution of precision 

(DOP) 
real time 8-2, 8-4, 8-11 
real-time kinematic (RTK) 1-18, 

8-15,8-16, 8-39, 8-45, B-5, 

B-11-13 
recon 2-8, 3-1 , 3-2, 6-4, 7-5, 1 1 -31 

communication 3-16 

description and sketch 3-12 

field 3-4 

monumentation 3-8 

office 3-3 

party 3-2 

report 3-16, 11-3 

requirements 3-1 

station description and sketch 
3-12 

transportation 3-16 
recording 5-6 
reference mark (RM) 3-5, 3-1 1 , 

3-12 
reference stake 6-4. See also 

reference mark (RM) 
relative DOP (RDOP) 8-19, 8-50. 

See also dilution of precision 

(DOP) 
relative positioning 8-30. See also 

differential positioning 
report 10-8, 10-10, 11-1, 11-8 

end-of-project 11-6, 11-13, 
11-30 

incident 11-7 

initial site-visitation trip (ISVT) 
11-2 

ISVT 11-3, 11-7, 11-15. See 
also initial site-visitation 
trip (ISVT) 

percentage-of-project- 
completion 11-13 

progress 11-6 

recon 11-3, 11-7, 11-17 
RM, see reference mark (RM) 
RMS, see root-mean-square 

(RMS) 
root-mean-square (RMS) 8-12, 

8-13,8-49,8-50 



RTCM, see Radio Technical 
Commission for Maritime 
(RTCM) 

RTK, see real-time kinematic 
(RTK) 

runway 10-2, 10-4, 10-5, 10-9 



S/A, see selective availability (S/A) 
S1 11-17, 11-20 

53 9-2, 9-3, 11-8, 11-14, 11-15, 

11-26 

54 11-17 
satellite 

elevation B-1 1 

sky plot 8-32 

survey 1-6 
satellite vehicle (SV) 8-36 
SCP, see survey control point 

(SCP) 
sea level coefficient (SLC) 6-7, 

C-15 
selective availability (S/A) 8-2, 8-5, 

8-6, 8-8, 8-36 
SEP, see spherical error probable 

(SEP) 
session designation 8-33 
SIC, see survey information center 

(SIC) 
SIF, see stadia-interval factor (SIF) 
signal. See also target; traverse 

5-21 , 6-4 
SLC, see sea level coefficient 

(SLC) 
software 8-37, 8-46, 8-54, 8-55, 

8-61,8-63, B-10, B-1 6 

traverse 8-53 
SOP, see standing operating 

procedure (SOP) 
space segment 8-2 
SPCE, see survey planning and 

coordination element (SPCE) 
SPCO, see survey planning and 

coordinating officer (SPCO) 
specially prepared hard surface 

(SPHS) 10-9 
spherical error probable (SEP) 

8-11,8-13 
spheroid 1-3 
SPHS, see specially prepared hard 

surface (SPHS) 
SPS, see Standard Positioning 

Service (SPS) 
spur shot 8-30 



SSGCN, see Standards and 

Specifications for Geodetic 

Control Networks (SSGCN) 
stadia-interval factor (SIF) 7-8, 7-9 
Standard Positioning Service 

(SPS) 1-4,8-2,8-4,8-5,8-36 
Standards and Specifications for 

Geodetic Control Networks 

(SSGCN) 2-3, 6-1 
standing operating procedure 

(SOP) 1-13, 1-14,2-5-7, 6-4, 

11-1, 11-6, 11-13, 11-14, 

11-18, 11-26 
static 8-1 , 8-2, 8-1 5-1 7, 8-21 , 8-24, 

8-27, 8-28, 8-30, 8-39-41 , 

8-44,8-45, B-5, B-10, B-1 1, 

B-1 4 
static surveying 1-9 
station 

designation 8-33, 8-34 

mark 5-6 

markers 6-3 

occupation 8-32 

traverse 6-3 
stop and go B-10 
stop-and-go kinematic, see 

kinematic, stop-and-go 
supplementary surveys 1-6 
survey 11-1, B-6, B-1 2, B-1 5, C-4, 

C-7 

airfield 10-1, 10-2, 10-8 

airfield obstruction 11-22 

AOC, see airport obstruction 
chart (AOC) 

artillery 9-1 

carrier-beat phase 8-47 
absolute 8-47 
relative 8-47 

computation C-1 

control 5-1 

construction 1-6 

conventional 8-21 

data 3-5 

DGPS 8-31, 8-37, 8-39 

differential 8-54 

engineering 8-39, 8-55 

equipment 1-8 

fieldwork 1-11 

geodetic 8-55 

geodetic control 8-18, 8-27 

GPS 8-25, 8-26, 8-28, 8-54. 
See also Global 
Positioning System 
(GPS) 

GPS control 8-27 



lndex-6 



FM 3-34.2 



NAVAID 1-6, 10-1, 10-2. See 
also navigational aid 
(NAVAID) 

notes 1-14, 1-15 
erasures 1-15 

obstruction 1 1-26. See also 
airport obstruction chart 
(AOC) 

project control 8-20 

rapid static 8-15, 8-16, 8-39, 
8-45, B-12, B-13 

team 6-4 

topographic 1-6, 8-20, 8-39, 
8-42,8-55,9-1, 11-13 

vertical-control 8-17 
survey control point (SCP) 1-1,1-3, 

1-5,3-3,3-11,5-3,5-6,5-8, 

5-10,9-1,9-2, 9-4, 11-4 
survey fieldwork 

accuracy 1-12 

equipment 1-11 

errors 1-12 

personnel 1-11 

progress 1-12 

purpose 1-12 

terrain 1-11 

weather 1-11 
survey information center (SIC) 

1-3, 1-9,3-3,9-2, 11-21 
survey missions 1-1 

deployable weapons 1-1 

intelligence 1-2 

joint-level operations 1-3 

National Imagery and 
Mapping Agency 1-1 

signal 1-2 

topographic missions 1-3 

United States Air Force 1-2 
survey operations 2-1 
survey planning and coordination 

element (SPCE) 9-1 , 9-2, 9-4 
surveying 8-16 
survey planning and coordinating 

officer (SPCO) 9-3 
SV, see satellite vehicle (SV) 



TA, see target acquisition (TA) 
TAB, see target acquisition battery 

(TAB) 
TACAN, see tactical air navigation 

(TACAN) 
tactical air navigation (TACAN) 

10-2 



target 5-16, 6-4 

AISI5-17. See also automated 
integrated survey 
instrument (AISI) 

lighted target sets 5-19 

optical-theodolite 5-16 

range-pole 5-19 

survey 5-21 

target and tribrach adjustment 
5-20 

setup 5-19 

tripod 5-19 
target acquisition battery (TAB) 9-1 
target acquisition (TA) 3-3, 9-3 
TDY, see temporary duty (TDY) 
TDZE, see touchdown zone 

elevation (TDZE) 
TEC, see Topographic 

Engineering Center (TEC) 
technical OPORD (TECHOPORD) 

11-2, 11-13, 11-15, 11-26. 

See also operation order 

(OPORD) 
TECHOPORD, see technical 

OPORD (TECHOPORD) 
temporary duty (TDY) 11-16,11-17 
temporary markers 3-6 
terrain analyst 1-3 
theodolite 5-1, 5-2 
three dimensional (3D) 8-2, 8-4, 

8-6,8-9,8-10,8-13,8-18, 

8-39-41 , 8-54, 8-56, 8-59-61 , 

8-65,8-66, B-7, B-9, B-16 
Topographic Engineering Center 

(TEC) 4-1 0,8-44, 11-14 
topographic survey 1 -6. See also 

survey 
topographic surveyor 1-1,1 -3-5, 

1-8, 1-9, 1-11-13,5-2,5-31, 

8-63, 9-1 
touchdown zone elevation (TDZE) 

10-2, 10-9, 10-10 
transitional surface 1 0-5 
transportation 3-16 
traverse 1-7, 1-16, 3-2, 5-28, 6-1, 

6-2, 6-4, 6-5, 6-7, 6-8, 8-20, 

8-27-29,8-41,8-51,8-53, 

8-58-61, 10-7, 11-21, 11-28, 

11-31, C-7, C-18, C-20-22 

closed 6-1 

closed on a second known 
point 6-2 

closure 8-51 

loop 6-2, 8-56 

open 6-1 



software 8-53 

stations 6-3 
traverse lines 3-4 
triangulation 3-1, 3-4, 8-20, 8-28 
trig lists 3-3 

trigonometric leveling 3-2 
trip report 2-9 
two dimensional (2D) 8-6, 8-1 1 , 

8-14,8-18,8-56,8-61 



U 

UDS, see user-defined sequence 

(UDS) 
UERE, see user equivalent range 

error (UERE) 
UHF, see ultrahigh frequency 

(UHF) 
ultrahigh frequency (UHF) 8-38 
United States Air Force (USAF) 

1-2, 1-9 
United States Army Aeronautical 

Services Agency (USAASA) 

1-2, 1-7, 10-1 
United States Army Engineer 

School (USAES) 1-5 
Universal Polar Stereographic 

(UPS) 4-3, 4-7 
universal time, coordinated (UTC) 

8-7, 8-32, 8-36 
Universal Transverse Mercator 

(UTM)4-3, 4-6, 5-14, C-7, 

C-11 
UPS, see Universal Polar 

Stereographic (UPS) 
US Army Corps of Engineers 

(USACE)2-3, 3-3, 3-8, 4-10 
US Coast Guard (USCG) 1-4, 8-38 
US Geologic Survey (USGS) 3-3, 

11-14 
US Military Grid-Reference System 

(MGRS) 4-6, 4-7 
US National Control Network 3-2 
USAASA, see United States Army 

Aeronautical Services Agency 

(USAASA) 
USACE, see US Army Corps of 

Engineers (USACE) 
USAF, see United States Air Force 

(USAF) 
USCG, see US Coast Guard 

(USCG) 
user equivalent range error 

(UERE) 8-9 



lndex-7 



FM 3-34.331 



user-defined sequence (UDS) 

5-27, 5-28 
USGS, see US Geologic Survey 

(USGS) 
UTC, see universal time, 

coordinated (UTC) 
UTM, see Universal Transverse 

Mercator (UTM) 
UTM grids. See also Universal 

Transverse Mercator (UTM) 

4-6 



VDOP, see vertical DOP 

vertical control 8-68 

vertical DOP (VDOP) 8-11,8-19. 

See also dilution of precision 

(DOP) 



vertical observations 5-10 
very-high frequency (VHF) 8-38 
VHF, see very-high frequency 

(VHF) 
VHF omnidirectional range (VOR) 

10-2 
VOR, see VHF omnidirectional 

range (VOR) 
VOR and TACAN (VORTAC) 10-2 
VORTAC, see VOR and TACAN 

(VORTAC) 



W 

warning order 11-14 

WGS, see World Geodetic System 

(WGS) 
WGS 84, see World Geodetic 

System 1984 (WGS 84) 



World Geodetic System (WGS) 

1-2,4-1,4-3,4-7 
World Geodetic System 1984 

(WGS 84) 1-2, 1-7,4-8,4-9, 

8-17,8-21,8-37,8-40,9-2, 

10-7, B-9 
World GEOREF System 4-7 

Y 

Y-code8-8, 8-38, B-12 



ZD, see zenith distance (ZD). See 
also vertical observations 

zenith 5-1 

zenith distance (ZD) 5-10, 5-13. 
See also vertical observations 



lndex-8 



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Field Sheet, Infrared 

For use of this form, see FM 3-34.331; the proponent agency Is TRADOC. 


PROJECT 


ORGANIZATION 


DATE 


APPROX DISTANCE 


ZERO CORRECTION * 


CALIBRATIONDATE 


Observer 


RECORDER 


INSTRUMENT STAY (ON 


H.I. 


ELEVATION 


ELEVATION 
INSTRUMENT 


ECCENTRICITY* 

TOWARD 

AWAY 


INST NO 


REFLECTOR STATION 


H.I. 


ELEVATION 


ELEVATION 
REFLECTOR 


ECCENTRICltY * 

TOWARD 

AWAY 


PAISM NO 


METEOROLOGICAL READINGS 


ZD INSTRUMENT TO REFLECTOR 




TIME 


PRESSURE 

(Hg) 


TEMP. 
(DRY) 


DISTANCE (meters) 


IN. 


F" 


1 






INSTRUMENT 








2 






REFLECTOR 








3 






SUM 






4 






MEAN 






5 






CORRECTION FACTOR (PPM) 




6 






PRODUCT = UD x PPM 

RC = PRODUCT x 10" 6 
T - UD ± Z ± RC 
H' = (T) 2 -(d) 2 
H' = SIN ZD x T 
Hft = H' X 3.280840 


7 






8 






9 






10 






SUM 






UD 




MEAN UNCORRECTED 
SLOPE DISTANCE (UD) 






PPM 




ZERO CORRECTION" (Z) 






PRODUCT 




REFRACTIVE INDEX 
DORRECTION (RC) 






RC 




DORRECTED SLOPE 
DISTANCE (T) 






DIFF. OF ELEV. (d) 




JNCORRECTED HORIZON. 
DISTANCE (H') 






° Obtained from Instrument Calibration. ( 
* Toward Eocentrlclty must be ADDED. - 
Away Eccentricity must be SUBTRACTED. 


ECCENTRIC 
DORRECTION * (EC) 






-IORIZON DISTANCE 
(Hm) / (Hft) 






REMARKS 


COMPUTED BY 


DATE 


CHECKED BY 


DATE 


PAGE OF 



DA Form 581 9-R, AUG 89 





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Three-Wire Leveling 

FM 3-34.331; the proponent ag 


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Airfield Compilation Report 

For use of this form, see FM 3-34.331; the proponent agency Is TRADOC. 



SURVEY AGENCY: 1 


AIRPORT NAME 


IDENTIFIER 




CITY 4 


STATE 

5 


EDITION 


SURVEY DATE 


AIRPORT 
REFERENCE POINT 


8 


LATITUDE 

9 


LONGITUDE 

10 


A CL OR ANGLE 

11 


AIRPORT 
LOCATION POINT 


12 


LATITUDE _ 
13 


LONGITUDE 

14 


DECLINATION 

15 


AIRPORT ELEVATION 
(In feet) 16 


CONTROL TOWER FLOOR 
LOCATED 17 ELEVATION (In feet) 18 


1. Field Survey 
19 DATUM POSITION CODE - 2. Photogrammetrlc 

3 .Other 


AIRPORT DATA 


ELEVATION 


LATITUDE 


LONGITUDE 


YR-CODE 


REMARKS 


OFFICE 
CODE 


20 


21 


22 


23 


24 


25 


26 














































































































































RUNWAY 


DSPLCD 

THR 
LENGTH 


RWYEND 
ELEVATION 


LATITUDE 


LONGITUDE 


WIDTH 
LENGTH 


GEODETIC AZ. IN) 


OFFICE 
CODE 


MAG. BEARING (N) 
















34 



















































































DA Form 5821-R, AUG 89 



AIRPORT NAME 



Precision Approach Radar (GCA) Data 

For use of this form, see FM 3-34.331; the proponent agency Is TRADOC, 



CITY 



STATE 



PAR COMPONENTS AND PERTINENT RUNWAY DATA 
Numbered items correspond to the diagram below. 



1. PAR Antenna 



2. Touchdown Reflector 



LATITUDE 



SURVEY DATE (Mo./Day/Year) 



LONGITUDE 



(1 / 100 Second) 



3. The point on runway C/L closest to the 
Touchdown Reflector (Item 2). 



4, Runway C/L End. 



5. Runway C/L End. 



6. The point on runway C/L closest to PAR Antenna. 



7. Displaced Threshold (If applicable). 



ELEVATION 



(1/10 Foot) 



I 



J- 



PAR Antenna - Enter Numeral 1 1n circle to Indicate PAR Antenna Position. 
Touchdown Reflector - Enter Numeral 2 in circle to Indicate Touohdown Reflector. 



PAR - GROUND DISTANCE 



3 to 7 

(If applicable) 



FEET 



1 to 6 



FEET 



3 to 6 



FEET 



2 to 3 



FEET 



3 to 4 



FEET 



GEODETIC AZIMUTH SOUTH 

' a 

4 to 5 



ADD APPLICABLE NUMBERS TO CIRCLES AND RUNWAY ENDS. SHOW NORTH ARROW. 




DA Form 5822-R, AUG 89 



Instrument Landing System Data 

For use of this form, see FM 3-34.331 ; the proponent agency Is TRADOC. 



AIRPORT NAME 



CITY 



STATE 



ILS COMPONENTS AND PERTINENT RUNWAY DATA 
Numbered items correspond to the diagram below. 



1. Localizer Antenna (Course Array): Point on ground 
beneath the localizer antenna. 



2. Glide Slope Indicator (GSt): Center of the base 
supporting the antenna. 



LATITUDE 



SURVEY DATE (Mo./Day/Year) 



LONGITUDE 



{1 1 100 Second) 



ELEVATION 



(1/10 Foot) 



3. The point on runway C/L closest to the base of the 
Glide Slope Indicator Antenna (Item 2). 



4. Runway C/L End. 



5. Runway C/L End. 



6. The point on runway C/L closest to the base of 
the offset Localizer (Case 2). 



GROUND DISTANCE 

TO 

END OF RUNWAY 



MARKERS 



LATITUDE 



LONGITUDE 



(1 / 10 Second) 



INNER OR B. C. MARKER (RUNWAY END) 



feet 



MIDDLE MARKER (RUNWAY END) 



feet 



OUTER MARKER (RUNWAY END) 



feet 



LOCALIZER - GROUND DISTANCE 



Case 1 (normal) 



Case 2 (offset) 



1to5 



FEET 



1 to 6 



FEET 



2to3 



FEET 



5 to 6 



FEET 



3 to 4 



FEET 



GEODETIC AZIMUTH SOUTH 
O ' » 

4 to 5 



ADD APPLICABLE NUMBERS TO CIRCLES AND RUNWAY ENDS. SHOW NORTH ARROW. 

Casel £) Case 2 ♦— ^*> 



© 




DA Form 5827-R, AUG 89 



FM 3-34.331 (FM 5-232) 
26January 2001 



By Order of the Secretary of the Army: 



ERIC K. SHINSEKI 

General, United States Army 
Chief of Staff 



Official: 



JOEL B.HUDSON 

Administrative Assistant to the 
Secretary of the Army 
0034601 



DISTRIBUTION: 

Active Army, Army National Guard, and US Army Reserve: To be distributed in accordance with the 
initial distribution number 1 1 0678, requirements for FM 3-34.331 . 



PIN: 078762-000